U.S. patent application number 16/623318 was filed with the patent office on 2020-06-04 for method and device for transmitting nprach preamble in narrowband iot system supporting frame structure type 2.
The applicant listed for this patent is LG Electronics Inc.. Invention is credited to Joonkui AHN, Daesung HWANG, Seunggye HWANG, Changhwan PARK, Seokmin SHIN.
Application Number | 20200178296 16/623318 |
Document ID | / |
Family ID | 64741718 |
Filed Date | 2020-06-04 |
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United States Patent
Application |
20200178296 |
Kind Code |
A1 |
SHIN; Seokmin ; et
al. |
June 4, 2020 |
METHOD AND DEVICE FOR TRANSMITTING NPRACH PREAMBLE IN NARROWBAND
IOT SYSTEM SUPPORTING FRAME STRUCTURE TYPE 2
Abstract
The present specification provides a method for transmitting a
narrowband physical random access channel (NPRACH) preamble in a
narrow band (NB)-Internet of things (IoT) system supporting a frame
structure type 2. More specifically, the method performed by a user
equipment includes receiving, from a base station, control
information related to an uplink-downlink configuration; and
transmitting, to the base station, the NPRACH preamble based on
parameters related to a NPRACH preamble transmission related to the
received control information.
Inventors: |
SHIN; Seokmin; (Seoul,
KR) ; PARK; Changhwan; (Seoul, KR) ; AHN;
Joonkui; (Seoul, KR) ; HWANG; Daesung; (Seoul,
KR) ; HWANG; Seunggye; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG Electronics Inc. |
Seoul |
|
KR |
|
|
Family ID: |
64741718 |
Appl. No.: |
16/623318 |
Filed: |
June 25, 2018 |
PCT Filed: |
June 25, 2018 |
PCT NO: |
PCT/KR2018/007179 |
371 Date: |
December 16, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62525155 |
Jun 26, 2017 |
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62565059 |
Sep 28, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 5/0012 20130101;
H04L 5/001 20130101; H04L 27/2607 20130101; H04W 74/004 20130101;
H04W 74/08 20130101; H04L 5/0053 20130101; H04L 5/00 20130101; H04W
74/00 20130101; H04W 72/0453 20130101; H04W 74/0833 20130101 |
International
Class: |
H04W 74/00 20090101
H04W074/00; H04L 5/00 20060101 H04L005/00; H04W 74/08 20090101
H04W074/08; H04L 27/26 20060101 H04L027/26; H04W 72/04 20090101
H04W072/04 |
Claims
1. A method for transmitting, by a user equipment, a narrowband
physical random access channel (NPRACH) preamble in a narrow band
(NB)-Internet of things (IoT) system supporting a frame structure
type 2, the method comprising: receiving, from a base station,
control information related to an uplink-downlink configuration;
and transmitting, to the base station, the NPRACH preamble based on
one or more parameters related to the received control information,
wherein the NPRACH preamble includes one or more symbol groups,
wherein one symbol group includes one cyclic prefix (CP) and at
least one symbol, wherein the one or more parameters include a
first parameter representing a number of symbols included in the
one symbol group and a second parameter representing a length of
the CP included in the one symbol group, wherein the first
parameter and the second parameter are configured to be different
from a third parameter and a fourth parameter respectively
corresponding to the first parameter and the second parameter, and
wherein the third parameter and the fourth parameter are parameters
related to a NPRACH preamble transmission supported in a frame
structure type 1.
2. The method of claim 1, wherein the one or more parameters are
differently configured according to uplink-downlink configuration
information supported by the base station.
3. The method of claim 1, wherein the first parameter and the
second parameter have a value less than the third parameter and the
fourth parameter, respectively.
4. The method of claim 3, wherein a value of the first parameter is
a natural number less than 5.
5. The method of claim 1, wherein the symbol groups are transmitted
through a first frequency hopping and a second frequency
hopping.
6. The method of claim 5, wherein a value of the second frequency
hopping is six times a value of the first frequency hopping.
7. The method of claim 1, wherein the one or more parameters
further include a fifth parameter representing a number of
consecutive symbol groups included in one preamble and a sixth
parameter representing a total number of symbol groups included in
the one preamble.
8. The method of claim 7, wherein a value of the fifth parameter is
2, and a value of the sixth parameter is 4.
9. A user equipment transmitting a narrowband physical random
access channel (NPRACH) preamble in a narrow band (NB)-Internet of
things (IoT) system supporting a frame structure type 2, the user
equipment comprising: a radio frequency (RF) module configured to
transmit and receive a radio signal; and a processor configured to
control the RF module, wherein the processor is configured to:
receive, from a base station, control information related to an
uplink-downlink configuration; and transmit, to the base station,
the NPRACH preamble based on one or more parameters related to the
received control information, wherein the NPRACH preamble includes
one or more symbol groups, wherein one symbol group includes one
cyclic prefix (CP) and at least one symbol, wherein the one or more
parameters include a first parameter representing a number of
symbols included in the one symbol group and a second parameter
representing a length of the CP included in the one symbol group,
wherein the first parameter and the second parameter are configured
to be different from a third parameter and a fourth parameter
respectively corresponding to the first parameter and the second
parameter, and wherein the third parameter and the fourth parameter
are parameters related to a NPRACH preamble transmission supported
in a frame structure type 1.
10. The user equipment of claim 9, wherein the one or more
parameters are differently configured according to uplink-downlink
configuration information supported by the base station.
Description
TECHNICAL FIELD
[0001] The present invention relates to a narrowband IoT system,
and more particularly to a method for transmitting a NPRACH
preamble in a narrowband IoT system supporting a frame structure
type 2 and a device therefor.
BACKGROUND ART
[0002] The mobile communication system is developed to provide the
voice service while guaranteeing the activity of a user. However,
the mobile communication system is extended to the data service in
addition to the voice service. Currently, since the shortage of
resource is caused owing to the explosive traffic increase and
users requires higher services, more developed mobile communication
system is needed.
[0003] The requirement for the next mobile communication system
should support the acceptance of explosive data traffic increase,
the innovative increase of transmission rate per user, the
acceptance of the number of connection devices which are
dramatically increased, very low End-to-End Latency, high energy
efficiency. To this end, various techniques have been researched
such as the Dual Connectivity, the Massive Multiple Input Multiple
Output (Massive MIMO), the In-band Full Duplex, the Non-Orthogonal
Multiple Access (NOMA), the Super wideband support, the Device
Networking, and so on.
DISCLOSURE
Technical Problem
[0004] An object of the present specification is to provide a
NPRACH preamble configuration method for transmitting a NPRACH
preamble using UL/DL configuration of legacy LTE when TDD is
supported in a NB-IoT system.
[0005] Technical problems to be solved by the present invention are
not limited by the above-mentioned technical problems, and other
technical problems which are not mentioned above can be clearly
understood from the following description by those skilled in the
art to which the present invention pertains.
Technical Solution
[0006] The present specification provides a method for
transmitting, by a user equipment, a narrowband physical random
access channel (NPRACH) preamble in a narrow band (NB)-Internet of
things (IoT) system supporting a frame structure type 2, the method
comprising receiving, from a base station, control information
related to an uplink-downlink configuration; and transmitting, to
the base station, the NPRACH preamble based on parameters related
to a NPRACH preamble transmission related to the received control
information, wherein the NPRACH preamble includes one or more
symbol groups, wherein one symbol group includes one cyclic prefix
(CP) and at least one symbol, wherein the parameters related to the
NPRACH preamble transmission include a first parameter representing
a number of symbols included in the one symbol group and a second
parameter representing a length of the CP included in the one
symbol group, wherein the first parameter and the second parameter
are configured to be different from a third parameter and a fourth
parameter respectively corresponding to the first parameter and the
second parameter, and wherein the third parameter and the fourth
parameter are parameters related to a NPRACH preamble transmission
supported in a frame structure type 1.
[0007] In the present specification, parameters related to the
NPRACH preamble are differently configured according to
uplink-downlink configuration information supported by the base
station.
[0008] In the present specification, the first parameter and the
second parameter have a value less than the third parameter and the
fourth parameter, respectively.
[0009] In the present specification, a value of the first parameter
is a natural number less than 5.
[0010] In the present specification, the symbol groups are
transmitted through a first frequency hopping and a second
frequency hopping.
[0011] In the present specification, a value of the second
frequency hopping is six times a value of the first frequency
hopping.
[0012] In the present specification, the parameters related to the
NPRACH preamble transmission further include a fifth parameter
representing a number of consecutive symbol groups included in one
preamble and a sixth parameter representing a total number of
symbol groups included in the one preamble.
[0013] In the present specification, a value of the fifth parameter
is 2, and a value of the sixth parameter is 4.
[0014] The present specification provides a user equipment
transmitting a narrowband physical random access channel (NPRACH)
preamble in a narrow band (NB)-Internet of things (IoT) system
supporting a frame structure type 2, the user equipment comprising
a radio frequency (RF) module configured to transmit and receive a
radio signal; and a processor configured to control the RF module,
wherein the processor is configured to receive, from a base
station, control information related to an uplink-downlink
configuration; and transmit, to the base station, the NPRACH
preamble based on parameters related to a NPRACH preamble
transmission related to the received control information, wherein
the NPRACH preamble includes one or more symbol groups, wherein one
symbol group includes one cyclic prefix (CP) and at least one
symbol, wherein the parameters related to the NPRACH preamble
transmission include a first parameter representing a number of
symbols included in the one symbol group and a second parameter
representing a length of the CP included in the one symbol group,
wherein the first parameter and the second parameter are configured
to be different from a third parameter and a fourth parameter
respectively corresponding to the first parameter and the second
parameter, and wherein the third parameter and the fourth parameter
are parameters related to a NPRACH preamble transmission supported
in a frame structure type 1.
Advantageous Effects
[0015] The present specification has an effect capable of using
UL/DL configuration of legacy LTE by defining a new NPRACH preamble
format when TDD is supported in a NB-IoT system.
[0016] Effects obtainable from the present invention are not
limited by the effects mentioned above, and other effects which are
not mentioned above can be clearly understood from the following
description by those skilled in the art to which the present
invention pertains.
DESCRIPTION OF DRAWINGS
[0017] The accompanying drawings, which are included to provide a
further understanding of the invention, illustrate embodiments of
the invention and together with the description serve to explain
the principle of the invention.
[0018] FIG. 1 illustrates a structure of a radio frame in a
wireless communication system to which the present invention is
applicable.
[0019] FIG. 2 illustrates a resource grid for one downlink slot in
a wireless communication system to which the present invention is
applicable.
[0020] FIG. 3 illustrates a structure of a downlink subframe in a
wireless communication system to which the present invention is
applicable.
[0021] FIG. 4 illustrates a structure of an uplink subframe in a
wireless communication system to which the present invention is
applicable.
[0022] FIG. 5 illustrates an example of a component carrier and
carrier aggregation in a wireless communication system to which the
present invention is applicable.
[0023] FIG. 6 illustrates a cell classification in a system
supporting carrier aggregation.
[0024] FIG. 7 illustrates an example of a symbol group of a NPRACH
preamble.
[0025] FIG. 8 illustrates an example of a NPRACH preamble format in
a NB-IoT system.
[0026] FIG. 9 illustrates an example of a repetition and random
hopping method of a NPRACH preamble.
[0027] FIG. 10 illustrates an example of a NPRACH preamble format
proposed by the present specification.
[0028] FIG. 11 illustrates an example of a hopping pattern for a
NPRACH preamble symbol group proposed by the present
specification.
[0029] FIG. 12 illustrates an example of a NPRACH preamble format
proposed by the present specification.
[0030] FIG. 13 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0031] FIG. 14 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0032] FIG. 15 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0033] FIG. 16 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0034] FIGS. 17 and 18 illustrate another example of a hopping
pattern for a NPRACH preamble symbol group proposed by the present
specification.
[0035] FIG. 19 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0036] FIG. 20 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0037] FIG. 21 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0038] FIG. 22 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0039] FIG. 23 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0040] FIG. 24 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0041] FIG. 25 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0042] FIG. 26 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0043] FIG. 27 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0044] FIG. 28 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0045] FIG. 29 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0046] FIG. 30 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0047] FIG. 31 illustrates an example of multi-tone NPRACH preamble
transmission proposed by the present specification.
[0048] FIG. 32 illustrates another example of multi-tone NPRACH
preamble transmission proposed by the present specification.
[0049] FIG. 33 illustrates another example of multi-tone NPRACH
preamble transmission proposed by the present specification.
[0050] FIG. 34 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0051] FIG. 35 illustrates an example of a short NPRACH preamble
format proposed by the present specification.
[0052] FIG. 36 illustrates another example of multi-tone NPRACH
preamble transmission proposed by the present specification.
[0053] FIG. 37 illustrates another example of multi-tone NPRACH
preamble transmission proposed by the present specification.
[0054] FIGS. 38 to 41 respectively illustrate other examples of
NPRACH preamble transmission proposed by the present
specification.
[0055] FIGS. 42 to 45 respectively illustrate other examples of
NPRACH preamble transmission proposed by the present
specification.
[0056] FIG. 46 illustrates another example of NPRACH preamble
transmission proposed by the present specification.
[0057] FIG. 47 illustrates another example of NPRACH preamble
transmission proposed by the present specification.
[0058] FIG. 48 illustrates another example of NPRACH preamble
transmission proposed by the present specification.
[0059] FIG. 49 illustrates an example of a symbol group shape
according to FIG. 48.
[0060] FIG. 50 illustrates an example of a method of interchanging
the transmission order between symbol groups of a NPRACH preamble
proposed by the present specification.
[0061] FIG. 51 illustrates an example of a phase pre-compensation
method for multi-tone transmission of a NPRACH preamble.
[0062] FIG. 52 is a flow chart illustrating an operation of a UE
for transmitting a NPRACH preamble proposed by the present
specification.
[0063] FIG. 53 illustrates a block configuration diagram of a
wireless communication device to which methods proposed by the
present specification are applicable.
[0064] FIG. 54 illustrates a block configuration diagram of a
communication device according to an embodiment of the present
invention.
[0065] FIG. 55 illustrates an example of a RF module of a wireless
communication device to which a method proposed by the present
specification is applicable.
[0066] FIG. 56 illustrates another example of a RF module of a
wireless communication device to which a method proposed by the
present specification is applicable.
MODE FOR INVENTION
[0067] Hereafter, preferred embodiments of the present invention
will be described in detail with reference to the accompanying
drawings. A detailed description to be disclosed hereinbelow
together with the accompanying drawing is to describe embodiments
of the present invention and not to describe a unique embodiment
for carrying out the present invention. The detailed description
below includes details in order to provide a complete
understanding. However, those skilled in the art know that the
present invention can be carried out without the details.
[0068] In some cases, in order to prevent a concept of the present
invention from being ambiguous, known structures and devices may be
omitted or may be illustrated in a block diagram format based on
core function of each structure and device.
[0069] In the specification, a base station means a terminal node
of a network directly performing communication with a terminal. In
the present document, specific operations described to be performed
by the base station may be performed by an upper node of the base
station in some cases. That is, it is apparent that in the network
constituted by multiple network nodes including the base station,
various operations performed for communication with the terminal
may be performed by the base station or other network nodes other
than the base station. A base station (BS) may be generally
substituted with terms such as a fixed station, Node B,
evolved-NodeB (eNB), a base transceiver system (BTS), an access
point (AP), and the like. Further, a `terminal` may be fixed or
movable and be substituted with terms such as user equipment (UE),
a mobile station (MS), a user terminal (UT), a mobile subscriber
station (MSS), a subscriber station (SS), an advanced mobile
station (AMS), a wireless terminal (WT), a Machine-Type
Communication (MTC) device, a Machine-to-Machine (M2M) device, a
Device-to-Device (D2D) device, and the like.
[0070] Hereinafter, a downlink means communication from the base
station to the terminal and an uplink means communication from the
terminal to the base station. In the downlink, a transmitter may be
a part of the base station and a receiver may be a part of the
terminal. In the uplink, the transmitter may be a part of the
terminal and the receiver may be a part of the base station.
[0071] Specific terms used in the following description are
provided to help appreciating the present invention and the use of
the specific terms may be modified into other forms within the
scope without departing from the technical spirit of the present
invention.
[0072] The following technology may be used in various wireless
access systems, such as code division multiple access (CDMA),
frequency division multiple access (FDMA), time division multiple
access (TDMA), orthogonal frequency division multiple access
(OFDMA), single carrier-FDMA (SC-FDMA), non-orthogonal multiple
access (NOMA), and the like. The CDMA may be implemented by radio
technology universal terrestrial radio access (UTRA) or CDMA2000.
The TDMA may be implemented by radio technology such as Global
System for Mobile communications (GSM)/General Packet Radio
Service(GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). The
OFDMA may be implemented as radio technology such as IEEE
802.11(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802-20, E-UTRA(Evolved
UTRA), and the like. The UTRA is a part of a universal mobile
telecommunication system (UMTS). 3rd generation partnership project
(3GPP) long term evolution (LTE) as a part of an evolved UMTS
(E-UMTS) using evolved-UMTS terrestrial radio access (E-UTRA)
adopts the OFDMA in a downlink and the SC-FDMA in an uplink.
LTE-advanced (A) is an evolution of the 3GPP LTE.
[0073] The embodiments of the present invention may be based on
standard documents disclosed in at least one of IEEE 802, 3GPP, and
3GPP2 which are the wireless access systems. That is, steps or
parts which are not described to definitely show the technical
spirit of the present invention among the embodiments of the
present invention may be based on the documents. Further, all terms
disclosed in the document may be described by the standard
document.
[0074] 3GPP LTE/LTE-A is primarily described for clear description,
but technical features of the present invention are not limited
thereto.
[0075] Overview of Wireless Communication System to which the
Present Invention is Applicable
[0076] FIG. 1 illustrates a structure of a radio frame in a
wireless communication system to which the present invention is
applicable.
[0077] 3GPP LTE/LTE-A supports radio frame structure type 1
applicable to frequency division duplex (FDD) and radio frame
structure type 2 applicable to time division duplex (TDD).
[0078] In FIG. 1, the size of a radio frame in a time domain is
represented as a multiple of a time unit of T_s=1/(15000*2048).
Downlink and uplink transmissions consist of a radio frame having a
duration of T_f=307200*T_s=10 ms.
[0079] FIG. 1(a) illustrates the radio frame structure type 1. The
radio frame structure type 1 is applicable to both full duplex FDD
and half duplex FDD.
[0080] A radio frame consists of 10 subframes. One radio frame
consists of 20 slots of T_slot=15360*T_s=0.5 ms length, and indexes
of 0 to 19 are given to the respective slots. One subframe consists
of two consecutive slots in the time domain, and subframe i
consists of slot 2i and slot 2i+1. A time required to transmit one
subframe is referred to as a transmission time interval (TTI). For
example, the length of one subframe may be 1 ms, and the length of
one slot may be 0.5 ms.
[0081] The uplink transmission and the downlink transmission in the
FDD are distinguished in the frequency domain. Whereas there is no
restriction in the full duplex FDD, a UE cannot transmit and
receive simultaneously in the half duplex FDD operation.
[0082] One slot includes a plurality of orthogonal frequency
division multiplexing (OFDM) symbols in the time domain and
includes a plurality of resource blocks (RBs) in a frequency
domain. Since 3GPP LTE uses OFDMA in downlink, OFDM symbols are
used to represent one symbol period. The OFDM symbol may be called
one SC-FDMA symbol or a symbol period. The resource block is a
resource allocation unit and includes a plurality of consecutive
subcarriers in one slot.
[0083] FIG. 1(b) illustrates frame structure type 2.
[0084] The radio frame type 2 consists of two half-frames of length
153600*T_s=5 ms each. Each half-frame consists of five subframes of
length 30720*T_s=1 ms.
[0085] In the frame structure type 2 of a TDD system,
uplink-downlink configuration is a rule indicating whether uplink
and downlink are allocated (or reserved) to all subframes.
[0086] Table 1 represents uplink-downlink configuration.
TABLE-US-00001 TABLE 1 Uplink- Downlink- Downlink to-Uplink config-
Switch-point Subframe number uration periodicity 0 1 2 3 4 5 6 7 8
9 0 5 ms D S U U U D S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S
U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S U U D D D D
D D 5 10 ms D S U D D D D D D D 6 5 ms D S U U U D S U U D
[0087] Referring to Table 1, for each subframe in a radio frame,
`D` represents a subframe for a downlink transmission, `U`
represent a subframe for an uplink transmission, `S` represents a
special subframe that includes three types, a Downlink Pilot Time
Slot (DwPTS), a Guard Period (GP) and an Uplink Pilot Time Slot
(UpPTS).
[0088] The DwPTS is used for an initial cell search,
synchronization or channel estimation in a terminal. The UpPTS is
used for the channel estimation in a BS and synchronizing an uplink
transmission synchronization of a terminal. The GP is a period for
removing interference occurred in uplink owing to multi-path
latency of a downlink signal between uplink and downlink.
[0089] Each subframe i includes slot 2i and slot 2i+1 of
T_slot=15360*T_s=0.5 ms length.
[0090] There are seven types of uplink-downlink configurations and
the position and/or number of downlink subframe, special subframe
and uplink subframe are different for each configuration.
[0091] The time switched from downlink to uplink or the time
switched from uplink to downlink is referred to as a switching
point. The periodicity of the switching point means a period in
which the phenomenon of unlink subframe and downlink subframe being
switched is repeated in the same pattern, and both 5 ms and 10 ms
are supported. In the case of a period of 5 ms downlink-uplink
switching point, the special subframe(s) is existed in every
half-frame, and in the case of a period of 10 ms downlink-uplink
switching point, the special subframe(s) is existed in the first
half-frame only.
[0092] For all configurations, 0th, fifth subframes and the DwPTS
are durations only for a downlink transmission. The subframe
directly following the UpPTS and subframe are durations for an
uplink transmission always.
[0093] Such an uplink-downlink configuration is the system
information, and may be known to a BS and a terminal. A BS may
notify the change of the uplink-downlink allocation state of a
radio frame by transmitting an index of configuration information
only whenever the uplink-downlink configuration information is
changed. In addition, the configuration information is a sort of
downlink control information and may be transmitted through a
Physical Downlink Control Channel (PDCCH) like other scheduling
information, or it is the broadcast information and may be commonly
transmitted to all terminals in a cell through a broadcast
channel.
[0094] Table 2 represents a configuration (lengths of
DwPTS/GP/UpPTS) of a special subframe.
TABLE-US-00002 TABLE 2 Normal cyclic prefix Extended cyclic prefix
in downlink in downlink UpPTS UpPTS Special Normal Extended Normal
Extended subframe cyclic prefix cyclic prefix cyclic prefix cyclic
prefix configuration DwPTS in uplink in uplink DwPTS in uplink in
uplink 0 6592 T.sub.s 2192 T.sub.s 2560 T.sub.s 7680 T.sub.s 2192
T.sub.s 2560 T.sub.s 1 19760 T.sub.s 20480 T.sub.s 2 21952 T.sub.s
23040 T.sub.s 3 24144 T.sub.s 25600 T.sub.s 4 26336 T.sub.s 7680
T.sub.s 4384 T.sub.s 5120 T.sub.s 5 6592 T.sub.s 4384 T.sub.s 5120
T.sub.s 20480 T.sub.s 6 19760 T.sub.s 23040 T.sub.s 7 21952 T.sub.s
-- -- -- 8 24144 T.sub.s -- -- --
[0095] The radio frame structure according to an example of FIG. 1
is just an example, but the number of subcarriers included in a
radio frame, the number of slots included in a subframe or the
number of OFDM symbols included in a slot may be changed in various
manners.
[0096] FIG. 2 illustrates a resource grid for one downlink slot in
a wireless communication system to which the present invention is
applicable.
[0097] Referring to FIG. 2, one downlink slot includes the
plurality of OFDM symbols in the time domain. Herein, it is
exemplarily described that one downlink slot includes 7 OFDM
symbols and one resource block includes 12 subcarriers in the
frequency domain, but the present invention is not limited
thereto.
[0098] Each element on the resource grid is referred to as a
resource element and one resource block includes 12.times.7
resource elements. The number of resource blocks included in the
downlink slot, NDL is subordinated to a downlink transmission
bandwidth.
[0099] A structure of the uplink slot may be the same as that of
the downlink slot.
[0100] FIG. 3 illustrates a structure of a downlink subframe in a
wireless communication system to which the present invention is
applicable.
[0101] Referring to FIG. 3, up to first three OFDM symbols in the
first slot of the subframe are a control region to which control
channels are allocated, and residual OFDM symbols are a data region
to which a physical downlink shared channel (PDSCH) is allocated.
Examples of downlink control channel used in the 3GPP LTE include a
Physical Control Format Indicator Channel (PCFICH), a Physical
Downlink Control Channel (PDCCH), a Physical Hybrid-ARQ Indicator
Channel (PHICH), and the like.
[0102] The PFCICH is transmitted in the first OFDM symbol of the
subframe and transports information on the number (i.e., the size
of the control region) of OFDM symbols used for transmission of the
control channels in the subframe. The PHICH which is a response
channel to the uplink transports an Acknowledgement
(ACK)/Not-Acknowledgement (NACK) signal for a hybrid automatic
repeat request (HARQ). Control information transmitted through a
PDCCH is referred to as downlink control information (DCI). The
downlink control information includes uplink resource allocation
information, downlink resource allocation information, or an uplink
transmission (Tx) power control command for a predetermined
terminal group.
[0103] The PDCCH may transport A resource allocation and
transmission format (also referred to as a downlink grant) of a
downlink shared channel (DL-SCH), resource allocation information
(also referred to as an uplink grant) of an uplink shared channel
(UL-SCH), paging information in a paging channel (PCH), system
information in the DL-SCH, resource allocation for an upper-layer
control message such as a random access response transmitted in the
PDSCH, an aggregate of transmission power control commands for
individual terminals in the predetermined terminal group, a voice
over IP (VoIP). A plurality of PDCCHs may be transmitted in the
control region and the terminal may monitor the plurality of
PDCCHs. The PDCCH is constituted by one or an aggregate of a
plurality of continuous control channel elements (CCEs). The CCE is
a logical allocation wise used to provide a coding rate depending
on a state of a radio channel to the PDCCH. The CCEs correspond to
a plurality of resource element groups. A format of the PDCCH and a
bit number of usable PDCCH are determined according to an
association between the number of CCEs and the coding rate provided
by the CCEs.
[0104] The base station determines the PDCCH format according to
the DCI to be transmitted and attaches the control information to a
cyclic redundancy check (CRC) to the control information. The CRC
is masked with a unique identifier (referred to as a radio network
temporary identifier (RNTI)) according to an owner or a purpose of
the PDCCH. In the case of a PDCCH for a specific terminal, the
unique identifier of the terminal, for example, a cell-RNTI
(C-RNTI) may be masked with the CRC. Alternatively, in the case of
a PDCCH for the paging message, a paging indication identifier, for
example, the CRC may be masked with a paging-RNTI (P-RNTI). In the
case of a PDCCH for the system information, in more detail, a
system information block (SIB), the CRC may be masked with a system
information identifier, that is, a system information (SI)-RNTI.
The CRC may be masked with a random access (RA)-RNTI in order to
indicate the random access response which is a response to
transmission of a random access preamble.
[0105] FIG. 4 illustrates a structure of an uplink subframe in a
wireless communication system to which the present invention is
applicable.
[0106] Referring to FIG. 4, the uplink subframe may be divided into
the control region and the data region in a frequency domain. A
physical uplink control channel (PUCCH) transporting uplink control
information is allocated to the control region. A physical uplink
shared channel (PUSCH) transporting user data is allocated to the
data region. One terminal does not simultaneously transmit the
PUCCH and the PUSCH in order to maintain a single carrier
characteristic.
[0107] A resource block (RB) pair in the subframe are allocated to
the PUCCH for one terminal. RBs included in the RB pair occupy
different subcarriers in two slots, respectively. The RB pair
allocated to the PUCCH frequency-hops in a slot boundary.
[0108] Carrier Aggregation
[0109] A communication environment considered in embodiments of the
present invention includes multi-carrier supporting environments.
That is, a multi-carrier system or a carrier aggregation system
used in the present invention means a system that aggregates and
uses one or more component carriers (CCs) having a smaller
bandwidth smaller than a target band at the time of configuring a
target wideband in order to support a wideband.
[0110] In the present invention, multi-carriers mean aggregation of
(or carrier aggregation) of carriers and in this case, the
aggregation of the carriers means both aggregation between
continuous carriers and aggregation between non-contiguous
carriers. Further, the number of component carriers aggregated
between the downlink and the uplink may be differently set. A case
in which the number of downlink component carriers (hereinafter,
referred to as `DL CC`) and the number of uplink component carriers
(hereinafter, referred to as `UL CC`) are the same as each other is
referred to as symmetric aggregation and a case in which the number
of downlink component carriers and the number of uplink component
carriers are different from each other is referred to as asymmetric
aggregation. The carrier aggregation may be used mixedly with a
term such as the carrier aggregation, the bandwidth aggregation,
spectrum aggregation, or the like.
[0111] The carrier aggregation configured by combining two or more
component carriers aims at supporting up to a bandwidth of 100 MHz
in the LTE-A system. When one or more carriers having the bandwidth
than the target band are combined, the bandwidth of the carriers to
be combined may be limited to a bandwidth used in the existing
system in order to maintain backward compatibility with the
existing IMT system. For example, the existing 3GPP LTE system
supports bandwidths of 1.4, 3, 5, 10, 15, and 20 MHz and a 3GPP
LTE-advanced system (i.e., LTE-A) may be configured to support a
bandwidth larger than 20 MHz by using on the bandwidth for
compatibility with the existing system. Further, the carrier
aggregation system used in the preset invention may be configured
to support the carrier aggregation by defining a new bandwidth
regardless of the bandwidth used in the existing system.
[0112] The LTE-A system uses a concept of the cell in order to
manage a radio resource.
[0113] The carrier aggregation environment may be called a
multi-cell environment. The cell is defined as a combination of a
pair of a downlink resource (DL CC) and an uplink resource (UL CC),
but the uplink resource is not required. Therefore, the cell may be
constituted by only the downlink resource or both the downlink
resource and the uplink resource. When a specific terminal has only
one configured serving cell, the cell may have one DL CC and one UL
CC, but when the specific terminal has two or more configured
serving cells, the cell has DL CCs as many as the cells and the
number of UL CCs may be equal to or smaller than the number of DL
CCs.
[0114] Alternatively, contrary to this, the DL CC and the UL CC may
be configured. That is, when the specific terminal has multiple
configured serving cells, a carrier aggregation environment having
UL CCs more than DL CCs may also be supported. That is, the carrier
aggregation may be appreciated as aggregation of two or more cells
having different carrier frequencies (center frequencies). Herein,
the described `cell` needs to be distinguished from a cell as an
area covered by the base station which is generally used.
[0115] The cell used in the LTE-A system includes a primary cell
(PCell) and a secondary cell (SCell). The P cell and the S cell may
be used as the serving cell. In a terminal which is in an
RRC_CONNECTED state, but does not have the configured carrier
aggregation or does not support the carrier aggregation, only one
serving constituted by only the P cell is present. On the contrary,
in a terminal which is in the RRC_CONNECTED state and has the
configured carrier aggregation, one or more serving cells may be
present and the P cell and one or more S cells are included in all
serving cells.
[0116] The serving cell (P cell and S cell) may be configured
through an RRC parameter. PhysCellId as a physical layer identifier
of the cell has integer values of 0 to 503. SCellIndex as a short
identifier used to identify the S cell has integer values of 1 to
7. ServCellIndex as a short identifier used to identify the serving
cell (P cell or S cell) has the integer values of 0 to 7. The value
of 0 is applied to the P cell and SCellIndex is previously granted
for application to the S cell. That is, a cell having a smallest
cell ID (or cell index) in ServCellIndex becomes the P cell.
[0117] The P cell means a cell that operates on a primary frequency
(or primary CC). The terminal may be used to perform an initial
connection establishment process or a connection re-establishment
process and may be designated as a cell indicated during a handover
process. Further, the P cell means a cell which becomes the center
of control associated communication among serving cells configured
in the carrier aggregation environment. That is, the terminal may
be allocated with and transmit the PUCCH only in the P cell thereof
and use only the P cell to acquire the system information or change
a monitoring procedure. An evolved universal terrestrial radio
access (E-UTRAN) may change only the P cell for the handover
procedure to the terminal supporting the carrier aggregation
environment by using an RRC connection reconfiguration message
(RRCConnectionReconfigutaion) message of an upper layer including
mobile control information (mobilityControlInfo).
[0118] The S cell means a cell that operates on a secondary
frequency (or secondary CC). Only one P cell may be allocated to a
specific terminal and one or more S cells may be allocated to the
specific terminal. The S cell may be configured after RRC
connection establishment is achieved and used for providing an
additional radio resource. The PUCCH is not present in residual
cells other than the P cell, that is, the S cells among the serving
cells configured in the carrier aggregation environment. The
E-UTRAN may provide all system information associated with a
related cell which is in an RRC_CONNECTED state through a dedicated
signal at the time of adding the S cells to the terminal that
supports the carrier aggregation environment. A change of the
system information may be controlled by releasing and adding the
related S cell and in this case, the RRC connection reconfiguration
(RRCConnectionReconfigutaion) message of the upper layer may be
used. The E-UTRAN may perform having different parameters for each
terminal rather than broadcasting in the related S cell.
[0119] After an initial security activation process starts, the
E-UTRAN adds the S cells to the P cell initially configured during
the connection establishment process to configure a network
including one or more S cells. In the carrier aggregation
environment, the P cell and the S cell may operate as the
respective component carriers. In an embodiment described below,
the primary component carrier (PCC) may be used as the same meaning
as the P cell and the secondary component carrier (SCC) may be used
as the same meaning as the S cell.
[0120] FIG. 5 illustrates an example of a component carrier and
carrier aggregation in the wireless communication system to which
the present invention is applicable.
[0121] FIG. 5(a) illustrates a single carrier structure used in an
LTE system. The component carrier includes the DL CC and the UL CC.
One component carrier may have a frequency range of 20 MHz.
[0122] FIG. 5(b) illustrates a carrier aggregation structure used
in the LTE system. In the case of FIG. 5(b), a case is illustrated,
in which three component carriers having a frequency magnitude of
20 MHz are combined. Each of three DL CCs and three UL CCs is
provided, but the number of DL CCs and the number of UL CCs are not
limited. In the case of carrier aggregation, the terminal may
simultaneously monitor three CCs, and receive downlink signal/data
and transmit uplink signal/data.
[0123] When N DL CCs are managed in a specific cell, the network
may allocate M (M.ltoreq.N) DL CCs to the terminal. In this case,
the terminal may monitor only M limited DL CCs and receive the DL
signal. Further, the network gives L (L.ltoreq.M.ltoreq.N) DL CCs
to allocate a primary DL CC to the terminal and in this case, UE
needs to particularly monitor L DL CCs. Such a scheme may be
similarly applied even to uplink transmission.
[0124] A linkage between a carrier frequency (or DL CC) of the
downlink resource and a carrier frequency (or UL CC) of the uplink
resource may be indicated by an upper-layer message such as the RRC
message or the system information. For example, a combination of
the DL resource and the UL resource may be configured by a linkage
defined by system information block type 2 (SIB2). In detail, the
linkage may mean a mapping relationship between the DL CC in which
the PDCCH transporting a UL grant and a UL CC using the UL grant
and mean a mapping relationship between the DL CC (or UL CC) in
which data for the HARQ is transmitted and the UL CC (or DL CC) in
which the HARQ ACK/NACK signal is transmitted.
[0125] FIG. 6 illustrates a cell classification in a system that
supports the carrier aggregation.
[0126] Referring to FIG. 6, a configured cell is a cell that should
be carrier-merged based on a measurement report among cells of a
base station as illustrated in FIG. 5, may be configured for each
terminal. The configured cell may reserve a resource for an
ACK/NACK transmission for a PDSCH transmission beforehand. An
activated cell is a cell that is configured to transmit PDSCH/PUSCH
actually among the configured cells, and performs a channel state
information (CSI) report for the PDSCH/PUSCH transmission and a
sounding reference signal (SRS) transmission. A de-activated cell
is a cell that does not perform the PDSCH/PUSCH transmission by a
command of the base station or a timer operation, may also stop the
CSI report and the SRS transmission.
[0127] A narrowband physical random access channel is described
below.
[0128] A physical layer random access preamble is based on
single-subcarrier frequency hopping symbol groups.
[0129] The symbol group is illustrated in FIG. 7 and includes a
cyclic prefix (CP) of length T.sub.CP and a sequence of 5 identical
symbols with total length T.sub.SEQ.
[0130] Parameters of the physical layer random access preamble are
listed in Table 3 below.
[0131] That is, FIG. 7 illustrates an example of a symbol group of
a NPRACH preamble, and Table 3 represents an example of random
access preamble parameters.
TABLE-US-00003 TABLE 3 Preamble format T.sub.CP T.sub.SEQ 0
2048T.sub.s 5 8192T.sub.s 1 8192T.sub.s 5 8192T.sub.s
[0132] The NPRACH preamble including 4 symbol groups transmitted
without gaps is transmitted N.sub.rep.sup.NPRACH times.
[0133] The transmission of a random access preamble, if triggered
by the MAC layer, is restricted to certain time and frequency
resources.
[0134] A NPRACH configuration provided by higher layers includes
the following parameters. [0135] NPRACH resource periodicity
N.sub.period.sup.NPRACH (nprach-Periodicity), [0136] frequency
location of the first subcarrier allocated to NPRACH
N.sub.scoffset.sup.NPRACH(nprach-SubcarrierOffset), [0137] the
number of subcarriers allocated to NPRACH N.sub.sc.sup.NPRACH
(nprach-NumSubcarriers), [0138] the number of starting subcarriers
allocated to contention based NPRACH random access
N.sub.sc_cont.sup.NPRACH (nprach-NumCBRA-StartSubcarriers), [0139]
the number of NPRACH repetitions per attempt N.sub.rep.sup.NPRACH
(numRepetitionsPerPreambleAttempt), [0140] NPRACH starting time
N.sub.start.sup.NPRACH (nprach-StartTime), [0141] fraction for
calculating starting subcarrier index for the range of NPRACH
subcarriers reserved for indication of UE support for multi-tone
msg3 transmission N.sub.MSG3.sup.NPRACH
(nprach-SubcarrierMSG3-RangeStart).
[0142] The NPRACH transmission can start only
N.sub.start.sup.NPRACH30720T.sub.s time units after the start of a
radio frame fulfilling n.sub.f
mod(N.sub.period.sup.NPRACH/10)=0.
[0143] After transmissions of 464(T.sub.CP+T.sub.SEQ) time units, a
gap of 4030720T.sub.s time units is inserted.
[0144] NPRACH configurations are invalid where
N.sub.scoffset.sup.NPRACH+N.sub.sc.sup.NPRACH>N.sub.sc.sup.UL.
[0145] The NPRACH starting subcarriers allocated to the contention
based random access are split into two sets of subcarriers, i.e.,
{0,1, . . . , N.sub.sc_cont.sup.NPRACHN.sub.MSG3.sup.NPRACH-1} and
{N.sub.sc_cont.sup.NPRACHN.sub.MSG3.sup.NPRACH, . . . ,
N.sub.sc_cont.sup.NPRACH-1}.
[0146] Here, if the second set is present, the second set indicates
UE support for multi-tone msg3 transmission.
[0147] A frequency location of the NPRACH transmission is
constrained within N.sub.sc.sup.RA=12 subcarriers. The frequency
hopping is used within the 12 subcarriers, and a frequency location
of an i-th symbol group is given by
n.sub.sc.sup.RA=n.sub.start+n.sub.SC.sup.RA(i), where
n.sub.start=N.sub.scoffset.sup.NPRACH+.left
brkt-bot.n.sub.init/N.sub.sc.sup.RA.right brkt-bot.N.sub.sc.sup.RA,
and conforms to Equation 1.
n ~ sc RA ( i ) = { ( n ~ sc RA ( 0 ) + i mod 4 = 0 and i > 0 f
( i / 4 ) mod N sc RA n ~ sc RA ( i - 1 ) + 1 i mod 4 = 1 , 3 and n
~ sc RA ( i - 1 ) mod 2 = 0 n ~ sc RA ( i - 1 ) - 1 i mod 4 = 1 , 3
and n ~ sc RA ( i - 1 ) mod 2 = 1 n ~ sc RA ( i - 1 ) + 6 i mod 4 =
2 and n ~ sc RA ( i - 1 ) < 6 n ~ sc RA ( i - 1 ) - 6 i mod 4 =
2 and n ~ sc RA ( i - 1 ) .gtoreq. 6 [ Equation 1 ] f ( t ) = ( f (
t - 1 ) + ( n = 10 t + 1 10 t + 9 c ( n ) 2 n - ( 10 t + 1 ) ) mod
( N sc RA - 1 ) + 1 ) mod N sc RA f ( - 1 ) = 0 ##EQU00001##
[0148] In Equation 1, n.sub.init is the subcarrier selected by the
MAC layer from {0,1, . . . , N.sub.sc.sup.NPRACH-1}. A pseudo
random generator is initialized with
c.sub.init=N.sub.ID.sup.Ncell.
[0149] Baseband Signal Generation
[0150] A time-continuous random access signal s.sub.i(t) for a
symbol group i is defined by Equation 2 below.
s i ( t ) = .beta. NPRACH e j 2 .pi. ( n SC RA ( i ) + Kk 0 + 1 / 2
) .DELTA. f RA ( t - T CP ) [ Equation 2 ] ##EQU00002##
[0151] Here, 0.ltoreq.t<T.sub.SEQ+T.sub.CP, .beta..sub.NPRACH,
is an amplitude scaling factor in order to conform to the transmit
power P.sub.NPRACH, k.sub.0=-N.sub.sc.sup.UL/2, and
K=.DELTA.f/.DELTA.f.sub.RA accounts for a difference in a
subcarrier spacing between the random access preamble and uplink
data transmission.
[0152] A location in the frequency domain is controlled by the
parameter n.sub.SC.sup.RA(i).
[0153] A variable .DELTA.f.sub.RA is given by Table 4 below.
[0154] That is, Table 4 represents an example of random access
baseband parameters.
TABLE-US-00004 TABLE 4 Preamble format .DELTA.f.sub.RA 0, 1 3.75
kHz
[0155] PUSCH-Config
[0156] IE PUSCH-ConfigCommon is used to designate a common PUSCH
configuration and a reference signal configuration for PUSCH and
PUCCH. IE PUSCH-ConfigDedicated is used to designate a UE-specific
PUSCH configuration.
TABLE-US-00005 TABLE 5 -- ASN1START TDD-PUSCH-UpPTS-r14 ::= CHOICE
{ release NULL, setup SEQUENCE { symPUSCH-UpPTS-r14 ENUMERATED
{sym1, sym2, sym3, sym4, sym5, sym6} OPTIONAL, -- Need ON
dmrs-LessUpPTS-r14 ENUMERATED {true} OPTIONAL -- Need OR } } --
ASN1STOP
[0157] In Table 5, symPUSCH-UpPTS represents the number of data
symbols configured for PUSCH transmission in UpPTS.
[0158] sym2, sym3, sym4, sym5, and sym6 values may be used for a
normal cyclic prefix, and sym1, sym2, sym3, sym4, and sym5 values
may be used for an extended cyclic prefix.
[0159] Mapping to Physical Resources
[0160] For UpPTS, if dmrsLess-UpPts is configured to `true`,
mapping to physical resources starts at
l=N.sub.symb.sup.UL-symPUSCH_UpPts symbol of a second slot of a
special subframe. Otherwise, the mapping to physical resources
starts at l=N.sub.symb.sup.UL-symPUSCH_UpPts-1 of the second slot
of the special subframe.
[0161] A method for designing a narrowband random access channel
(NRACH) preamble is described below when frame structure Type 2
(TDD) is supported in a narrowband (NB)-Internet of Things (IoT)
system supporting cellular IoT proposed by the present
specification.
[0162] Narrowband (NB)-LTE refers to a system for supporting low
complexity and low power consumption, which has a system bandwidth
corresponding to one physical resource block (PRB) of a LTE
system.
[0163] This may be mainly used for a communication scheme for
implementing Internet of things (IoT) by supporting a device such
as machine-type communication (MTC) in a cellular system.
[0164] The NB-IoT system has an advantage in that frequencies can
be efficiently used by using the same OFDM parameters, such as
subcarrier spacing, as those in the LTE system and allocating 1 PRB
for NB-LTE to a legacy LTE band without additional band
allocation.
[0165] In case of downlink, a physical channel of NB-LTE is defined
as NPSS/NSSS, NPBCH, NPDCCH/NEPDCCH, NPDSCH, etc. and is named by
adding N in order to distinguish the NB-LTE from the LTE.
[0166] A NPRACH preamble used in frequency division duplex (FDD)
NB-IoT up to Rel.14 has two formats, and a detailed shape thereof
is illustrated in FIG. 8.
[0167] That is, FIG. 8 illustrates an example of a NPRACH preamble
format in the NB-IoT system.
[0168] Referring to FIG. 8, a NPRACH preamble performs a single
tone transmission, has a subcarrier spacing of 3.75 kHz, and forms
one symbol group by a combination of five symbols and one CP.
[0169] In this instance, NPRACH preamble format 0 consists of 66.66
us CP and five consecutive 266.66 us symbols, and NPRACH preamble
format 1 consists of 266.66 us CP and five consecutive 266.66 us
symbols.
[0170] A length of a symbol group of the NPRACH preamble format 0
is 1.4 ms, and a length of a symbol group of the NPRACH preamble
format 1 is 1.6 ms.
[0171] A basic unit for repetition gathers four symbol groups to
form a single repetition.
[0172] Thus, a length of four consecutive symbol groups forming the
single repetition is 5.6 ms in the NPRACH preamble format 0 and is
6.4 ms in the NPRACH preamble format 1.
[0173] Further, as illustrated in FIG. 9, the NPRACH preamble is
configured to perform a first hopping with a spacing that is equal
to a subcarrier spacing and a second hopping with a spacing that is
six times the subcarrier spacing.
[0174] FIG. 9 illustrates an example of a repetition and random
hopping method of a NPRACH preamble.
[0175] In frame structure type 2 (TDD) to be introduced in Rel. 15
NB-IoT system, it is not easy to use, as it is, a legacy
NB-IoT(Rel. 14) NPRACH preamble format considering a UL/DL
configuration of legacy LTE.
[0176] However, although a TDD standalone mode may be configured to
use the legacy NB-IoT NPRACH preamble format by introducing a new
UL/DL configuration, an in-band mode or a guard band mode, which
has been generally considered, is not easy to use the legacy NB-IoT
NPRACH preamble format as it is.
[0177] Accordingly, the present specification provides a method for
designing the NPRACH preamble when the frame structure type 2 is
applied to the NB-IoT system.
[0178] Even in the following embodiments, the idea of the present
invention can be applied to channels other than PRACH and can be
extended to a multi-tone transmission scheme as well as a
single-tone transmission scheme.
[0179] Further, although the present specification has been
described focusing on the TDD in-band mode or the guard band mode,
it is obvious that methods proposed by the present specification
can be used in the standalone mode.
[0180] Enhanced NPRACH Preamble for Frame Structure Type 2
(TDD)
[0181] As illustrated in FIG. 9 above, it is advantageous to
configure the first hopping and the second hopping to be
transmitted in consecutive UL subframes, in terms of
performance.
[0182] However, if a legacy NPRACH preamble format is used even in
the TDD, there is no UL/DL configuration (see Table 1) capable of
consecutively transmitting four symbol groups.
[0183] Therefore, when a NPRACH preamble is designed in the TDD, it
may be considered to (1) reduce the number of symbols to be
included in one symbol group, (2) reduce a symbol length while
increasing a subcarrier spacing, or (3) reduce a CP length.
[0184] Alternatively, the NPRACH preamble may be designed by
combining the (1) to (3) described above.
[0185] Table 6 represents consecutive UL subframes per each
configuration in the UL/DL configuration of Table 2.
TABLE-US-00006 TABLE 6 Uplink- Downlink- Downlink to-Uplink config-
Switch-point Subframe number uration periodicity 0 1 2 3 4 5 6 7 8
9 0 5 ms D S U U U D S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S
U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S U U D D D D
D D 5 10 ms D S U D D D D D D D 6 5 ms D S U U U D S U U D
[0186] Referring to Table 6, if it is checked how many UL SFs
(subframes) can be consecutively used in the legacy UL/DL
configuration, configurations #0, #1, #3, #4, and #6 except for
configurations #2 and #5 each include at least two consecutive UL
subframes.
[0187] Further, considering UpPTS of a special subframe (it is
possible to configure up to 6 symbols), up to 428 us (71.33 us*6)
can be further used.
[0188] In this instance, a legacy LTE/MTC system has been
configured to respective UEs via dedicated signaling referred to as
symPUSCH-UpPTS.
[0189] Assuming that a TDD NPRACH preamble can be used in UpPTS,
the number of symbols included in the UpPTS can be configured
cell-specifically and semi-statistically through a system
information block (SIB).
[0190] In addition, because it is determined how many symbols can
be used in the UpPTS depending on a special subframe configuration
value, the number of UpPTS symbols for TDD NPRACH preamble that is
semi-statistically configured through the SIB may be based on (or
dependent on) the special subframe configuration.
[0191] That is, it may be configured such that the UpPTS is used in
NPARCH preamble transmission only in a previously promised special
subframe configuration (e.g., #0 and #5).
[0192] Further, when NPRACH resource allocation information is sent
to the UE, the UE may explicitly inform of whether the UpPTS can be
used for the NPRACH transmission.
[0193] In addition, the UE may be configured to implicitly indicate
whether to use the UpPTS by transmitting an UpPTS symbol parameter
for the TDD NPRACH preamble.
[0194] In this case, if it is configured to use the UpPTS, the UE
may be configured to transmit the NPRACH preamble from the
beginning of an UpPTS symbol configured from a base station.
[0195] Alternatively, if it is configured not to use the UpPTS, the
UE may be configured to transmit the NPRACH preamble to an UL
subframe start point located immediately after a special
subframe.
[0196] In addition, if the UE is informed that the UpPTS symbol can
be used for the NPRACH preamble, or even if not, the UE may be
configured to start the NPRACH preamble transmission at a NPRACH
preamble transmission start time configured by the base station if
the base station separately configures the NPRACH preamble
transmission start time.
[0197] Further, a method may be considered to secure an implicit
guard time by configuring, by the base station, TA (time from a
downlink time synchronization time to a time at which the NPRACH is
transmitted in advance) per CE level and/or per NPRACH format
(repetition number within the symbol group).
[0198] In this instance, an applied default TA may be configured
not to conform to NPRACH resources transmitting the NPRACH and
conform to default TA of resource minimally transmitting the
NPRACH.
[0199] In addition, if the base station informs the UE that the
NPRACH preamble can be transmitted in the UpPTS, or if the NPRACH
preamble transmission in the UpPTS is previously promised between
the UE and the base station, the following methods may be
considered.
[0200] First, a small gap hopping (e.g., a hopping with a gap equal
to a subcarrier spacing, for example, 3.75 kHz) may be configured
to be performed within the NPRACH preamble transmitted over a UpPTS
of a special SF and up to an UL SF immediately following the
special SF.
[0201] Characteristically, a cyclic prefix (CP) in the symbol group
of the PRACH preamble may be configured to be lengthened and
used.
[0202] Second, if the numbers of consecutive UL subframes are not
the same within 10 msec (e.g., UL/DL configuration #6 consisting of
three consecutive UL subframes and two consecutive UL subframes),
it may be configured to increase the CP of the symbol group in a
longer duration of UL subframes which consecutively appear, and
perform the small gap hopping.
[0203] Last, as a length of the UpPTS symbol capable of
transmitting the NPRACH preamble varies, a length of the CP in the
symbol group may be configured to vary.
[0204] Further, it may be configured such that the number of
symbols in the symbol group varies depending on the length of the
UpPTS symbol capable of transmitting the NPRACH preamble.
[0205] In addition, it may be considered that the UE selects and
transmits a NPRACH preamble format depending on the UL/DL
configuration that the cell configures to the UE.
[0206] Characteristically, the UE may be configured to select the
NPRACH preamble format depending on a minimum value of the number
of consecutively appearing UL subframes among the UL/DL
configurations.
[0207] The UL/DL configurations may be divided into case 1 in which
a minimum value of the number of consecutively appearing UL
subframes is 3 SFs in the UL/DL configurations #0 and #3, case 2 in
which a minimum value of the number of consecutively appearing UL
subframes is 2 SFs in the UL/DL configurations #1, #4 and #6, and
case 3 in which a minimum value of the number of consecutively
appearing UL subframes is 1 SF in the UL/DL configurations #2 and
#5.
[0208] The UE may be configured to select a different NPRACH
preamble format for each of the three cases.
[0209] Hereinafter, when the frame structure type 2 is applied to
the NB-IoT system, various methods related to the design of the
NRACH preamble are described in more detail.
[0210] (Method 1)
[0211] Method 1 is a method for increasing a subcarrier spacing of
a NPRACH preamble by N times than the existing one (i.e., a symbol
duration is reduced by 1/N times than the existing one) and
reducing a CP length by 1/T than the existing one.
[0212] That is, the Method 1 is a method for down-scaling the
symbol duration by N times while there is no change in the number
of symbols in a symbol group.
[0213] The Method 1 is to increase the subcarrier spacing of the
NPRACH preamble by N times than a subcarrier spacing value of a
legacy NPRACH preamble.
[0214] In this instance, it may be configured such that a symbol
length is reduced by 1/N times, and a considered CP length is
reduced by 1/T, where N is a positive integer and T is a real
number.
[0215] The Method 1 is described in more detail by way of example.
In the following examples, N and T can have different values.
Embodiment 1
[0216] Embodiment 1 is an example in which N=2 and T=2.
[0217] When a value of N is 2, a subcarrier spacing of a new NPRACH
preamble is 7.5 kHz that is two times 3.75 kHz.
[0218] At the same time, a symbol duration is reduced to 1/2 times
from 266.66 us to 133.33 us.
[0219] Since T is 2, a CP length is reduced to 1/2 times. Even in
this case, if CPs of two different lengths are supported, and
symbol number included in one symbol group is the same as a
structure of a legacy NPRACH preamble, new PRACH preamble format 0
and new PRACH preamble format 1 may be configured as illustrated in
FIG. 10.
[0220] FIG. 10 illustrates an example of a NPRACH preamble format
proposed by the present specification.
[0221] Referring to FIG. 10, a length of a symbol group forming the
PRACH preamble format 0 is 0.7 ms, and a length of a symbol group
forming the PRACH preamble format 1 is 0.8 ms.
[0222] That is, because a length of two consecutive symbol groups
is less than 2 ms even if the PRACH preamble format 1 is used, the
two symbol groups can be consecutively transmitted.
[0223] Thus, in this case, when each UE transmits a NPRACH
preamble, two symbol groups forming a first hopping may be
configured to be consecutively transmitted to two UL SFs, and a
second hopping may be configured to be transmitted between two
consecutive UL SFs.
[0224] This is illustrated as the following FIG. 11.
[0225] FIG. 11 illustrates an example of a hopping pattern for a
NPRACH preamble symbol group proposed by the present
specification.
[0226] Referring to FIG. 11, a total of k subcarriers from a
subcarrier n to a subcarrier n+k-1 have been allocated as frequency
resources for a NPRACH preamble, and it illustrates how the NPRACH
preamble is transmitted according to the situation of UL/DL
configuration #1 of legacy LTE TDD.
[0227] When the NPRACH preamble is transmitted in this manner,
performance degradation due to change in channel may occur as
compared to consecutively transmitting four symbol groups.
[0228] However, because the two symbol groups forming the first
hopping are consecutively transmitted, TA estimation per UE at a
base station end can proceed without major problems.
[0229] However, because the subcarrier spacing of the NPRACH
preamble has increased, there is a drawback in that the frequency
resources decrease as compared to the existing one.
[0230] That is, 48 frequency resources were available in case of
the existing 3.75 kHz subcarrier spacing, but 24 frequency
resources can be used in case of 7.5 kHz subcarrier spacing.
[0231] Further, as a CP length shortens, there may be a drawback of
a reduction in a cell coverage that the corresponding cell can
serve.
Embodiment 2
[0232] Embodiment 2 is an example in which N=4 and T=4.
[0233] When a value of N is 4, a subcarrier spacing of a new NPRACH
preamble is 15 kHz that is four times 3.75 kHz.
[0234] At the same time, a symbol duration is reduced to 1/4 times
from 266.66 us to 66.66 us. Further, since T is 4, a CP length is
reduced to 1/4 times.
[0235] Even in this case, if CPs of two different lengths are
supported, and symbol number included in one symbol group is the
same as a structure of a legacy NPRACH preamble, new PRACH preamble
format 0 and new PRACH preamble format 1 may be configured as
illustrated in FIG. 12.
[0236] FIG. 12 illustrates an example of a NPRACH preamble format
proposed by the present specification.
[0237] Referring to FIG. 12, a length of a symbol group forming the
PRACH preamble format 0 is 0.35 ms, and a length of a symbol group
forming the PRACH preamble format 1 is 0.4 ms.
[0238] That is, because a length of four consecutive symbol groups
is less than 2 ms even if the PRACH preamble format 1 is used, the
four symbol groups can be consecutively transmitted.
[0239] Thus, in this case, when each UE transmits a NPRACH
preamble, four symbol groups forming a first hopping and a second
hopping may be configured to be consecutively transmitted to two UL
SFs, similar to an existing method.
[0240] This is illustrated as the following FIG. 13.
[0241] FIG. 13 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0242] Referring to FIG. 13, a total of j subcarriers from a
subcarrier n to a subcarrier n+j-1 have been allocated as frequency
resources for a NPRACH preamble, and it illustrates how the NPRACH
preamble is transmitted according to the situation of UL/DL
configuration #1 of legacy LTE TDD.
[0243] When the NPRACH preamble is transmitted in this manner, TA
estimation per UE at a base station end can proceed without major
problems because the four symbol groups are consecutively
transmitted.
[0244] However, because the subcarrier spacing of the NPRACH
preamble has increased, there is a drawback in that the frequency
resources decrease as compared to the existing one.
[0245] That is, 48 frequency resources were available in case of
the existing 3.75 kHz subcarrier spacing, but 12 frequency
resources can be used in case of 15 kHz subcarrier spacing.
[0246] Further, as the CP length shortens, there may be a drawback
of a reduction in a cell coverage that the corresponding cell can
serve.
Embodiment 3
[0247] Embodiment 3 is an example in which N=2 and T=1.
[0248] When a value of N is 2, a subcarrier spacing of a new NPRACH
preamble is 7.5 kHz that is two times 3.75 kHz.
[0249] At the same time, a symbol duration is reduced to 1/2 times
from 266.66 us to 133.33 us. However, since T is 1, a CP length
does not change.
[0250] Even in this case, if CPs of two different lengths are
supported, and symbol number included in one symbol group is the
same as a structure of a legacy NPRACH preamble, new PRACH preamble
format 0 and new PRACH preamble format 1 may be configured as
illustrated in FIG. 14.
[0251] FIG. 14 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0252] Referring to FIG. 14, a length of a symbol group forming the
PRACH preamble format 0 is 0.733 ms, and a length of a symbol group
forming the PRACH preamble format 1 is 0.933 ms.
[0253] That is, because a length of two consecutive symbol groups
is less than 2.214 ms (2 UL SFs+3 symbols for UpPTS) even if the
PRACH preamble format 1 is used, the two symbol groups can be
consecutively transmitted.
[0254] Thus, in this case, when each UE transmits a NPRACH
preamble, two symbol groups forming a first hopping may be
configured to be consecutively transmitted to the UpPTS and two UL
SFs, and a second hopping may be configured to be transmitted to
appear between the UpPTS and two consecutive UL SFs. This is
illustrated as the following FIG. 15.
[0255] FIG. 15 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0256] Referring to FIG. 15, a total of k subcarriers from a
subcarrier n to a subcarrier n+k-1 have been allocated as frequency
resources for a NPRACH preamble, and it illustrates how the NPRACH
preamble is transmitted according to the situation of UL/DL
configuration #1 of legacy LTE TDD.
[0257] When the NPRACH preamble is transmitted in this manner,
performance degradation due to change in channel may occur as
compared to consecutively transmitting four symbol groups.
[0258] However, because the two symbol groups forming the first
hopping are consecutively transmitted, TA estimation per UE at a
base station end can proceed without major problems.
[0259] Because the subcarrier spacing of the NPRACH preamble has
increased, there is a drawback in that the frequency resources
decrease as compared to the existing one. That is, 48 frequency
resources were available in case of the existing 3.75 kHz
subcarrier spacing, but 24 frequency resources can be used in case
of 7.5 kHz subcarrier spacing. However, because the CP length does
not change, there is an advantage in that a cell coverage can
maintain the same level as a coverage of a FDD cell.
Embodiment 4
[0260] Embodiment 4 is an example in which N=4 and T=1.
[0261] When a value of N is 4, a subcarrier spacing of a new NPRACH
preamble is 15 kHz that is four times 3.75 kHz. At the same time, a
symbol duration is reduced to 1/4 times from 266.66 us to 66.66
us.
[0262] However, since T is 1, a CP length does not change. Even in
this case, if CPs of two different lengths are supported, and
symbol number included in one symbol group is the same as a
structure of a legacy NPRACH preamble, new PRACH preamble format 0
and new PRACH preamble format 1 may be configured as illustrated in
FIG. 16.
[0263] FIG. 16 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0264] According to FIG. 16, a length of a symbol group forming the
PRACH preamble format 0 is 0.4 ms, and a length of a symbol group
forming the PRACH preamble format 1 is 0.6 ms.
[0265] It may be configured to mainly use the PRACH preamble format
0 on the assumption that a coverage of a cell using UL/DL
configuration #2 is not generally large.
[0266] Thus, because a length of two consecutive symbol groups is
less than 1 ms in case of using the PRACH preamble format 0, the
two symbol groups can be consecutively transmitted.
[0267] Thus, in this case, when each UE transmits a NPRACH
preamble, two symbol groups forming a first hopping may be
configured to be consecutively transmitted to one UL SF, and two
symbol groups forming a second hopping may be also configured to be
consecutively transmitted to one UL SF.
[0268] This is illustrated in FIGS. 17 and 18 as follows.
[0269] FIGS. 17 and 18 illustrate another example of a hopping
pattern for a NPRACH preamble symbol group proposed by the present
specification.
[0270] Referring to FIGS. 17 and 18, a total of j subcarriers from
a subcarrier n to a subcarrier n+j-1 have been allocated as
frequency resources for a NPRACH preamble, and they illustrate how
the NPRACH preamble is transmitted according to the situation of
UL/DL configuration #2 of legacy LTE TDD.
[0271] Further, G symbol groups may be contained in a single
repetition.
[0272] FIG. 17 illustrates an example in which a symbol group is
contained in a single repetition four times, and FIG. 18
illustrates an example in which a symbol group is contained in a
single repetition eight times.
[0273] Characteristically, when a subcarrier spacing is 15 kHz, the
first hopping may be configured to hop by a difference of a single
tone (i.e., 15 kHz), and the second hopping may be configured to
hop by a difference of two tones (i.e., 30 kHz).
[0274] When the NPRACH preamble is transmitted in this manner,
performance degradation due to change in channel may occur as
compared to consecutively transmitting four symbol groups. However,
because the two symbol groups forming the first hopping and the two
symbol groups forming the second hopping each are consecutively
transmitted, TA estimation per UE at a base station end can proceed
without major problems.
[0275] However, because the subcarrier spacing of the NPRACH
preamble has increased, there is a drawback in that the frequency
resources decrease as compared to the existing one.
[0276] That is, 48 frequency resources were available in case of
the existing 3.75 kHz subcarrier spacing, but 12 frequency
resources can be used in case of 15 kHz subcarrier spacing.
[0277] However, because a CP length has not changed, there is an
advantage in that a cell coverage can maintain the same level as a
coverage of a FDD cell.
[0278] In addition, in the same situation, an example of a cell
using UL/DL configuration #1 is illustrated as the following FIG.
13.
[0279] (Method 2)
[0280] Method 2 is a method for changing the number of symbols
forming a symbol group of a NPRACH preamble to M.
[0281] Here, M is a natural number of M<5, and in the Method 2,
a subcarrier spacing, a symbol duration, and a CP length are not
changed.
[0282] That is, the Method 2 changes the number of symbols forming
the symbol group of the NPRACH preamble from the existing five to M
less than five.
[0283] Hereinafter, the Method 2 is described in more detail by way
of example.
Embodiment 1
[0284] Embodiment 1 is an example in which M=3.
[0285] When M is 3, it means that the number of symbols forming one
symbol group is 3. Because a subcarrier spacing does not change,
new PRACH preamble format 0 and new PRACH preamble format 1 may be
configured as illustrated in FIG. 19 if two different CP lengths
are used as it is.
[0286] FIG. 19 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0287] According to FIG. 19, a length of a symbol group forming the
PRACH preamble format 0 is 0.866 ms, and a length of a symbol group
forming the PRACH preamble format 1 is 1.066 ms.
[0288] That is, because a length of two consecutive symbol groups
is less than 2.428 ms (2 UL SFs+6 symbols for UpPTS) even if the
PRACH preamble format 1 is used, the two symbol groups can be
consecutively transmitted.
[0289] Thus, when each UE transmits a NPRACH preamble, two symbol
groups forming a first hopping may be configured to be
consecutively transmitted to the UpPTS and two UL SFs, and a second
hopping may be configured to be transmitted to appear between the
UpPTS and two consecutive UL SFs.
[0290] This is illustrated as the following FIG. 20. Referring to
FIG. 20, a total of 12 subcarriers from a subcarrier n to a
subcarrier n+11 have been allocated as frequency resources for a
NPRACH preamble, and it illustrates how the NPRACH preamble is
transmitted according to the situation of UL/DL configuration #1 of
legacy LTE TDD.
[0291] When the NPRACH preamble is transmitted in this manner,
performance degradation due to change in channel may occur as
compared to consecutively transmitting four symbol groups. However,
because the two symbol groups forming the first hopping are
consecutively transmitted, TA estimation per UE at a base station
end can proceed without major problems.
[0292] Further, because the subcarrier spacing has not changed, the
frequency resources have not changed, and also because the CP
length has not changed, there is an advantage in that a cell
coverage can be maintained.
[0293] However, because the number of symbols has decreased as
compared to an existing preamble, energy may decrease and thus a
repetition number required to achieve the same performance may
increase.
[0294] An implicit guard time may be configured to be longer than
the CP length, in order to maintain the cell coverage due to the CP
length.
[0295] Accordingly, in the example of FIG. 20, if UpPTS 6 symbols
are configured, the cell coverage can be maintained because the
implicit guard time (i.e., 294.66 us, 2428-2133.33=294.66 (us)) is
configured to be longer than the CP (i.e., 66.66 us or 266.66 us)
length.
[0296] FIG. 20 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
Embodiment 2
[0297] Embodiment 2 is an example in which M=2.
[0298] When M is 2, the number of symbols forming one symbol group
is 2. Because a subcarrier spacing does not change, new PRACH
preamble format 0 and new PRACH preamble format 1 may be configured
as illustrated in FIG. 21 if two different CP lengths are used as
it is.
[0299] FIG. 21 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0300] Referring to FIG. 21, a length of a symbol group forming the
PRACH preamble format 0 is 0.6 ms, and a length of a symbol group
forming the PRACH preamble format 1 is 0.8 ms.
[0301] That is, because a length of two consecutive symbol groups
is less than 2 ms even if the PRACH preamble format 1 is used, the
two symbol groups can be consecutively transmitted.
[0302] Thus, when each UE transmits a NPRACH preamble, two symbol
groups forming a first hopping may be configured to be
consecutively transmitted to two UL SFs, and a second hopping may
be configured to be transmitted to appear between two consecutive
UL SFs.
[0303] This is illustrated as the following FIG. 22.
[0304] FIG. 22 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0305] Referring to FIG. 22, a total of 12 subcarriers from a
subcarrier n to a subcarrier n+11 have been allocated as frequency
resources for a NPRACH preamble, and it illustrates how the NPRACH
preamble is transmitted according to the situation of UL/DL
configuration #1 of legacy LTE TDD.
[0306] When the NPRACH preamble is transmitted in this manner,
performance degradation due to change in channel may occur as
compared to consecutively transmitting four symbol groups. However,
because the two symbol groups forming the first hopping are
consecutively transmitted, TA estimation per UE at a base station
end can proceed without major problems.
[0307] Further, because the subcarrier spacing has not changed, the
frequency resources have not changed, and also because the CP
length has not changed, there is an advantage in that a cell
coverage can be maintained.
[0308] However, because the number of symbols decreases as compared
to an existing PRACH preamble, energy may decrease and thus a
repetition number required to achieve the same performance may
increase. Further, this embodiment has an advantage of maintaining
the cell coverage without additionally configuring the UpPTS as
compared to the example of M=3 described above.
[0309] (Method 3)
[0310] Method 3 is a method for changing the number of symbols
forming a symbol group of a NPRACH preamble to M and changing a CP
length.
[0311] Here, M is a natural number of M<5.
[0312] In the Method 3, a subcarrier spacing and a symbol duration
are not changed.
[0313] That is, the Method 3 changes the number of symbols forming
the symbol group of the NPRACH preamble from the existing five to M
less than five and also changes the CP length.
[0314] Hereinafter, the Method 3 is described in more detail by way
of example.
Embodiment 1
[0315] Embodiment 1 is an example in which M=3.
[0316] When M is 3, the number of symbols forming one symbol group
is 3. Considering that 66.66 us, 133.33 us, and 200 us are used as
a value of CP length (because a subcarrier spacing has not
changed), new PRACH preamble format 0, new PRACH preamble format 1,
and new PRACH preamble format 2 may be configured as illustrated in
FIG. 23.
[0317] FIG. 23 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0318] If only two CP lengths are used as different CP lengths like
characteristics of the FDD, it may be configured to use the PRACH
preamble format 0 as a default and to use only one of the PRACH
preamble format 1 and the PRACH preamble format 2.
[0319] Referring to FIG. 23, a length of a symbol group forming the
PRACH preamble format 0 is 0.866 ms, a length of a symbol group
forming the PRACH preamble format 1 is 0.933 ms, and a length of a
symbol group forming the PRACH preamble format 2 is 1 ms.
[0320] That is, because a length of two consecutive symbol groups
is less than 2.214 ms (2 UL SFs+3 symbols for UpPTS) even if the
PRACH preamble format 2 is used, the two symbol groups can be
consecutively transmitted.
[0321] Thus, when each UE transmits a NPRACH preamble, two symbol
groups forming a first hopping may be configured to be
consecutively transmitted to the UpPTS and two UL SFs, and a second
hopping may be configured to be transmitted to appear between the
UpPTS and two consecutive UL SFs.
[0322] This is illustrated in FIG. 24 as follows.
[0323] FIG. 24 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0324] Referring to FIG. 24, a total of 12 subcarriers from a
subcarrier n to a subcarrier n+11 have been allocated as frequency
resources for a NPRACH preamble, and it illustrates how the NPRACH
preamble is transmitted according to the situation of UL/DL
configuration #1 of legacy LTE TDD.
[0325] When the NPRACH preamble is transmitted in the method
illustrated in FIG. 24, performance degradation due to change in
channel may occur as compared to consecutively transmitting four
symbol groups.
[0326] Because the two symbol groups forming the first hopping are
consecutively transmitted, TA estimation per UE at a base station
end can proceed without major problems.
[0327] Further, because the subcarrier spacing has not changed, the
frequency resources have not changed, and also because the CP
length has not changed, there is an advantage in that a cell
coverage can be maintained.
[0328] However, because the number of symbols has decreased as
compared to an existing PRACH preamble, energy may decrease and
thus a repetition number required to achieve the same performance
may increase.
[0329] An implicit guard time may be configured to be longer than
the CP length, in order to maintain the cell coverage due to the CP
length.
[0330] Accordingly, in the example of FIG. 24, if UpPTS 3 symbols
are configured, the cell coverage can be maintained because the
implicit guard time (i.e., 214 us, 2214-2000=214 (us)) is
configured to be longer than the CP (i.e., 66.66 us or 133.33 us or
200 us) length.
[0331] (Method 4)
[0332] Method 4 is a combination of the Method 1 and the Method 2
and is a method for increasing a subcarrier spacing of a NPRACH
preamble by N times than the existing one (i.e., reducing a symbol
duration and a CP length by 1/N times than the existing one) and
changing the number of symbols forming a symbol group of a NPRACH
preamble to M.
[0333] Here, M is a natural number of M<5.
[0334] That is, the Method 4 may be a method of combining a method
for increasing the subcarrier spacing of the NPRACH preamble by N
times than a subcarrier spacing value of a legacy NPRACH preamble
according to the Method 1 mentioned above and a method for changing
the number of symbols forming the symbol group of the NPRACH
preamble from the existing five to M less than five according to
the Method 2 mentioned above.
[0335] In this instance, it may be configured such that a symbol
length is reduced by 1/N times, and a considered CP length is
reduced by 1/N.
[0336] Here, N is a positive integer, and M is a natural number
less than 5.
[0337] Hereinafter, the Method 4 is described in more detail by way
of example.
Embodiment 1
[0338] Embodiment 1 is an example in which N=2 and M=4.
[0339] When a value of N is 2, a subcarrier spacing of a new NPRACH
preamble is 7.5 kHz that is two times 3.75 kHz. At the same time, a
symbol duration is reduced to 1/2 times from 266.66 us to 133.33
us. Further, a CP length is reduced to 1/2 times.
[0340] In addition, when that M is 4, it means that the number of
symbols forming one symbol group is 4. Therefore, even in this
case, if CPs of two different lengths are supported, new PRACH
preamble format 0 and new PRACH preamble format 1 may be configured
as illustrated in FIG. 25.
[0341] FIG. 25 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0342] Referring to FIG. 25, a length of a symbol group forming the
PRACH preamble format 0 is 0.566 ms, and a length of a symbol group
forming the PRACH preamble format 1 is 0.666 ms.
[0343] That is, because a length of two consecutive symbol groups
is less than 2 ms even if the PRACH preamble format 1 is used, the
two symbol groups can be consecutively transmitted.
[0344] Thus, when each UE transmits a NPRACH preamble, two symbol
groups forming a first hopping may be configured to be
consecutively transmitted to two UL SFs, and a second hopping may
be configured to be transmitted to appear between two consecutive
UL SFs.
[0345] This is illustrated in FIG. 26 as follows.
[0346] FIG. 26 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0347] Referring to FIG. 26, a total of k subcarriers from a
subcarrier n to a subcarrier n+k-1 have been allocated as frequency
resources for a NPRACH preamble, and it illustrates how the NPRACH
preamble is transmitted according to the situation of UL/DL
configuration #1 of legacy LTE TDD.
[0348] When the NPRACH preamble is transmitted in this manner,
performance degradation due to change in channel may occur as
compared to consecutively transmitting four symbol groups. However,
because the two symbol groups forming the first hopping are
consecutively transmitted, TA estimation per UE at a base station
end can proceed without major problems.
[0349] Because the subcarrier spacing of the NPRACH preamble has
increased, there is a drawback in that the frequency resources
decrease as compared to the existing one.
[0350] That is, 48 frequency resources were available in case of
the existing 3.75 kHz subcarrier spacing, but 24 frequency
resources can be used in case of 7.5 kHz subcarrier spacing.
[0351] Further, as the CP length shortens, there is a drawback of a
reduction in the cell coverage that the corresponding cell can
serve. Because the number of symbols has decreased as compared to
the existing preamble, energy may decrease and thus a repetition
number required to achieve the same performance may increase.
Embodiment 2
[0352] Embodiment 2 is an example in which N=2 and M=3.
[0353] When a value of N is 2, a subcarrier spacing of a new NPRACH
preamble is 7.5 kHz that is two times 3.75 kHz.
[0354] At the same time, a symbol duration is reduced to 1/2 times
from 266.66 us to 133.33 us. Further, a CP length is reduced to 1/2
times.
[0355] In addition, when M is 3, the number of symbols forming one
symbol group is 3. Therefore, even in this case, if CPs of two
different lengths are supported, new PRACH preamble format 0 and
new PRACH preamble format 1 may be configured as illustrated in
FIG. 27.
[0356] FIG. 27 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0357] Referring to FIG. 27, a length of a symbol group forming the
PRACH preamble format 0 is 0.433 ms, and a length of a symbol group
forming the PRACH preamble format 1 is 0.533 ms.
[0358] That is, because a length of four consecutive symbol groups
is less than 2.28533 ms (2 UL SFs+4 symbols for UpPTS) even if the
PRACH preamble format 1 is used, the four symbol groups can be
consecutively transmitted.
[0359] Thus, in this case, when each UE transmits a NPRACH
preamble, four symbol groups forming a first hopping and a second
hopping may be configured to be consecutively transmitted to the
UpPTS and two UL SFs, similar to an existing method.
[0360] This is illustrated as the following FIG. 28.
[0361] FIG. 28 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0362] Referring to FIG. 28, a total of k subcarriers from a
subcarrier n to a subcarrier n+k-1 have been allocated as frequency
resources for a NPRACH preamble, and it illustrates how the NPRACH
preamble is transmitted according to the situation of UL/DL
configuration #1 of legacy LTE TDD.
[0363] When the NPRACH preamble is transmitted in this manner, four
symbol groups are consecutively transmitted. Therefore, TA
estimation per UE at a base station end can proceed without major
problems.
[0364] Because the subcarrier spacing of the NPRACH preamble has
increased, there is a drawback in that the frequency resources
decrease as compared to the existing one. That is, 48 frequency
resources were available in case of the existing 3.75 kHz
subcarrier spacing, but 24 frequency resources can be used in case
of 7.5 kHz subcarrier spacing.
[0365] Further, as the CP length shortens, there is a drawback of a
reduction in the cell coverage that the corresponding cell can
serve. Because the number of symbols has decreased as compared to
the existing preamble, energy may decrease and thus a repetition
number required to achieve the same performance may increase.
[0366] An implicit guard time may be configured to be longer than
the CP length, in order to maintain the cell coverage due to the CP
length.
[0367] Accordingly, in the corresponding example, if UpPTS 4
symbols are configured, the cell coverage can be maintained because
the implicit guard time (i.e., 152 us, 2285.33-2133.33=152 (us)) is
configured to be longer than the CP (i.e., 66.66 us or 133.33 us)
length.
[0368] (Method 5)
[0369] Method 5 relates to multi-tone NPRACH transmission for a TDD
NB-IoT system.
[0370] If the Methods 1 to 4 mentioned above have considered a
single tone in PRACH transmission, a TDD NPRACH may be configured
such that the above proposed methods (the Methods 1 to 4) use
multi-tone transmission.
[0371] In this instance, multi-tones may be contiguous or
non-contiguous.
[0372] In addition, a multi-tone configuration may be a
configuration in which contiguous and non-contiguous multi-tones
coexist. Hereinafter, the Method 5 is described in more detail by
way of example.
Embodiment 1
[0373] Embodiment 1 relates to non-contiguous dual tone
transmission.
[0374] Considering an example in which a dual tone is
non-contiguously transmitted, it is as follows.
[0375] A starting subcarrier resource to which a first tone will be
transmitted may be configured to select one among regions
configured with system information (SI), and a second tone may be
configured to be transmitted away from the first tone by a
previously promised frequency spacing or a certain frequency
spacing (e.g., 6 subcarrier spacings) configured with the SI.
[0376] That is, it may be considered that a first hopping of a
legacy NPRACH is maintained as it is, and a second hopping appears
as a dual tone.
[0377] In this case, a unit of repetition may be also configured as
a dual tone of two consecutive symbol groups and may be configured
to determine a tone, to which the first tone will move, through a
pseudo random hopping and to transmit the second tone away from the
first tone by a certain frequency spacing as mentioned above.
[0378] If it goes beyond a configured frequency resource region, it
may be configured to wrap-around in the frequency resource
region.
[0379] In case of the Embodiment 2 of the Method 2 mentioned above
(method for changing the number of symbols forming a symbol group
of a NPRACH preamble to two), an example of non-contiguous dual
tone transmission may be as the following FIG. 29.
[0380] FIG. 29 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0381] Referring to FIG. 29, a total of 12 subcarriers from a
subcarrier n to a subcarrier n+11 have been allocated as frequency
resources for a NPRACH preamble, and it illustrates how the NPRACH
preamble is transmitted according to the situation of UL/DL
configuration #1 of legacy LTE TDD.
[0382] If the NPRACH preamble is transmitted using this method,
there is a disadvantage in terms of PAPR and resource allocation.
However, an improvement of performance for preamble reception can
be expected by additionally transmitting symbols, of which
transmission has been insufficient with only a single tone, with
the dual tone.
[0383] Further, a length of single repetition decreases, and thus
an effect of a latency reduction can be obtained.
Embodiment 2
[0384] Embodiment 2 relates to contiguous triple tone
transmission.
[0385] Considering an example in which a triple tone is
contiguously transmitted, it is as follows.
[0386] A starting subcarrier resource to which a first tone will be
transmitted may be configured to select one among regions
configured with SI, and a second tone and a third tone may be
configured to be contiguously transmitted in increments of one tone
from the first tone.
[0387] If it goes beyond a configured frequency resource region, it
may be configured to wrap-around in the frequency resource
region.
[0388] In case of contiguous multi-tone, multi-tone preambles of
two symbol groups forming a first hopping may be configured to be
consecutively transmitted to two UL SFs, and a second hopping may
be configured to be transmitted to appear between two consecutive
UL SFs.
[0389] A contiguous multi-tone scheme for the case of the
Embodiment 2 of the Method 2 mentioned above (a method for changing
the number of symbols forming a symbol group of a NPRACH preamble
to two) is illustrated as the following FIG. 30.
[0390] FIG. 30 illustrates another example of a hopping pattern for
a NPRACH preamble symbol group proposed by the present
specification.
[0391] Referring to FIG. 30, a total of 12 subcarriers from a
subcarrier n to a subcarrier n+11 have been allocated as frequency
resources for a NPRACH preamble, and it illustrates how the NPRACH
preamble is transmitted according to the situation of UL/DL
configuration #1 of legacy LTE TDD.
[0392] If the NPRACH preamble is transmitted using this method,
there is a disadvantage in terms of PAPR and resource allocation.
However, an improvement of performance for preamble reception can
be expected by additionally transmitting symbols, of which
transmission has been insufficient with only a single tone, with
the multi-tone.
[0393] In addition, if a multi-tone NPRACH preamble is defined, an
operation of a UE capable of transmitting the multi-tone NPRACH
preamble needs to be defined more clearly.
[0394] Currently, Rel. 14 NB-IoT system has already supported
multi-tone transmission in message 3 (msg. 3, UE.fwdarw.eNB
transmission), and the UE capable of multi-tone transmission
selects a NPRACH preamble resource, that has been promised in
advance that the msg. 3 can be transmitted with the multi-tone, and
transmits a single tone preamble.
[0395] If Rel. 15 NB-IoT supports multi-tone preamble transmission,
the eNB may be configured to, for backward compatibility, configure
(A) NPRACH preamble resource that has been promised in advance that
the msg. 3 can be transmitted with the single-tone, (B) NPRACH
preamble resource that has been promised in advance that the msg. 3
can be transmitted with the multi-tone, and (C) multi-tone NPRACH
preamble resource that has been promised in advance that the msg. 3
can be transmitted with the multi-tone.
[0396] Thus, in this case, the UE that is capable of the multi-tone
transmission and satisfies a threshold of a repetition number
configured to the (C) resource may be configured to start the
NPRACH preamble transmission in the (C) resource.
[0397] If the UE does not receive a random access response (RAR) or
msg. 4 from the eNB, the UE may be configured to move to the (C)
resource corresponding to the following repetition number and
transmit the NPRACH preamble.
[0398] However, there is no (C) resource corresponding to the
following repetition number, the UE may be configured to move to
the (B) resource and transmit the NPRACH preamble.
[0399] If there is no (B) resource or a threshold of a repetition
number of the (B) resource is not satisfied, the UE may be
configured to transmit the NPRACH preamble in the (A) resource.
[0400] The subsequent operation is the same as the RACH operation
of the existing Rel. 13.
[0401] It is obvious that the UE using the (C) resource is capable
of the multi-tone transmission in the msg. 3.
[0402] In addition, if a preamble can be transmitted using
previously secured resources as in contention free (CF) NPRACH
transmission, it may be considered to contiguously transmit all of
multi-tones that the corresponding resources can use.
[0403] For example, if NPRACH resources previously secured to the
UE, that will perform the contention free NPRACH transmission
through the NPDCCH order, are K subcarriers, the UE may be
configured to transmit the NPRACH preamble to one UL SF using
contiguous K multi-tones.
[0404] Characteristically, K value may be 12, 24, 36, 48, etc.
[0405] This transmission is illustrated as the following FIG.
31.
[0406] FIG. 31 illustrates an example of multi-tone NPRACH preamble
transmission proposed by the present specification.
[0407] In this instance, the NPRACH preamble used in K tones may
have a specific sequence form of length K.
[0408] For example, a sequence with a good PAPR performance, such
as length-K ZC sequence, may be selected.
[0409] In addition, it may be configured such that a specific
sequence and a scrambling sequence different from the specific
sequence are multiplied by an element wise product to represent
different sequences.
[0410] Characteristically, the scrambling sequence may select a
sequence such as a PN sequence. If this method is used, contention
free transmission is performed. Therefore, there is an advantage in
that uplink synchronization can be adapted by using a less
repetition number than the existing one using all the previously
secured resources.
Embodiment 3
[0411] Embodiment 3 relates to NPRACH transmission using contiguous
and non-contiguous triple tone.
[0412] Considering an example in which the triple tone is
transmitted in the form in which contiguous and non-contiguous of
the triple tone coexist, it is as follows. A starting subcarrier
resource to which a first tone will be transmitted may be
configured to select one among regions configured with SI, a second
tone may be configured to be contiguously transmitted in increments
of one tone from the first tone, and a third tone may be configured
to be transmitted away from the second tone by a previously
promised frequency spacing or a certain frequency spacing (e.g., 6
subcarrier spacings) configured with the SI.
[0413] If it goes beyond a configured frequency resource region, it
may be configured to wrap-around in the frequency resource
region.
[0414] In case of contiguous/non-contiguous multi-tone, multi-tone
preambles of symbol groups forming a first hopping and a second
hopping may be configured to be transmitted to one UL SF.
[0415] A contiguous/non-contiguous multi-tone scheme for the case
of the Embodiment 2 of the Method 2 (a method for changing the
number of symbols forming a symbol group of a NPRACH preamble to
two) is illustrated as the following FIG. 32.
[0416] FIG. 32 illustrates another example of multi-tone NPRACH
preamble transmission proposed by the present specification.
[0417] Referring to FIG. 32, a total of 12 subcarriers from a
subcarrier n to a subcarrier n+11 have been allocated as frequency
resources for a NPRACH preamble, and it illustrates how the NPRACH
preamble is transmitted according to the situation of UL/DL
configuration #2 of legacy LTE TDD.
[0418] If the NPRACH preamble is transmitted using this method,
there is a disadvantage in terms of PAPR and resource allocation.
However, an improvement of performance for preamble reception can
be expected by additionally transmitting NPRACH symbols, of which
transmission has been insufficient with only a single tone, with
the multi-tone.
Embodiment 4
[0419] Embodiment 4 relates to different numerologies for
multi-tone NPRACH preamble transmission.
[0420] In addition, considering an example in which a multi-tone is
transmitted contiguously and non-contiguously, it is as
follows.
[0421] At a timing at which a multi-tone (e.g., dual tone) is first
transmitted contiguously, the multi-tone is transmitted using a
relatively small subcarrier spacing (i.e., SCS). A starting
subcarrier resource to which a first tone will be transmitted may
be configured to select one among regions configured with SI, and a
second tone may be configured to be contiguously transmitted in
increments of one tone (one tone basis is configured with SCS) from
the first tone.
[0422] At a timing at which a next multi-tone (e.g., dual tone) is
transmitted, the multi-tone is transmitted using a relatively large
subcarrier spacing (i.e., SCL). A starting subcarrier resource to
which a first tone will be transmitted may be configured to select
one among regions configured with SI, and a second tone may be
configured to be contiguously transmitted in increments of one tone
(one tone basis is configured with SCL) from the first tone.
[0423] Characteristically, the SCL may be M times the SCS. For
example, the SCS may be 3.75 kHz, and the SCL may be 22.5 kHz that
is six times the SCS. Further, when the multi-tone is transmitted
using the SCL, the multi-tone may be configured to be transmitted
applying a fractional offset.
[0424] In this instance, the fractional offset may select one among
M (=SCL/SCS) values, and if M is an even number, the fractional
offset may be determined as the following {-(0.5+(M/2-1))*SCS,
-(0.5+(M/2-2))*SCS, . . . , -(0.5+2)*SCS, -(0.5+1)*SCS,
-(0.5+0)*SCS, +(0.5+0)*SCS, +(0.5+1)*SCS, +(0.5+2)*SCS, . . . ,
+(0.5+(M/2-2))*SCS, +(0.5+(M/2-1))*SCS}.
[0425] Further, if M is an odd number, the fractional offset may be
determined as the following {-(.left brkt-bot.M/2.right
brkt-bot.)*SCS, -(.left brkt-bot.M/2.right brkt-bot.-1)*SCS,
-(.left brkt-bot.M/2.right brkt-bot.-2)*SCS, . . . , -2*SCS, -SCS,
0, +SCS, +2*SCS, . . . , +(.left brkt-bot.M/2.right
brkt-bot.-2)*SCS, +(.left brkt-bot.M/2.right brkt-bot.-1)*SCS,
+(.left brkt-bot.M/2.right brkt-bot.)*SCS}.
[0426] More specifically, for example, if the SCS is 3.75 kHz and
the SCL is 22.5 kHz, 3.75 kHz subcarrier spacing may come into 22.5
kHz subcarrier spacing 6 times. Therefore, M is 6, and one value
among {-9.375 kHz, -5.625 kHz, -1.875 kHz, +1.875 kHz, +5.625 kHz,
+9.375 kHz} from the center of the 22.5 kHz subcarrier spacing is
selected and is determined as the fractional offset. The multi-tone
may be configured to be transmitted moving by the fractional offset
from the center of the subcarrier spacing.
[0427] In this instance, the fractional offset may be configured to
be selected at the same location as the starting subcarrier
resource, to which the first tone will be transmitted, when the
multi-tone is transmitted using the SCS. This transmission method
is illustrated as the following FIG. 33.
[0428] FIG. 33 illustrates another example of a multi-tone NPRACH
preamble transmission proposed by the present specification.
[0429] In addition, a symbol group corresponding to an example of
using different numerologies is illustrated as the following FIG.
34.
[0430] FIG. 34 illustrates another example of a NPRACH preamble
format proposed by the present specification.
[0431] Referring to FIG. 34, when 3.75 kHz subcarrier spacing is
used, the number of symbols forming a symbol group is 2, and one CP
comes into the 3.75 kHz subcarrier spacing.
[0432] Further, when 22.5 kHz subcarrier spacing is used to adapt a
total length of preamble per each format, the number of symbols
forming a symbol group is 12 that is M times greater than the 3.75
kHz subcarrier spacing, and a CP of the same length as used in the
above preamble comes into the 22.5 kHz subcarrier spacing.
[0433] Characteristically, the corresponding CP may be configured
to consist of several symbols.
[0434] (Method 6)
[0435] Method 6 relates to short NPRACH preamble transmission for a
TDD NB-IoT system.
[0436] In addition, considering a NPRACH short format even in TDD
of NB-IoT for similar reasons to why the NPRACH short format is
implemented in TDD of legacy LTE, it is as follows.
[0437] The NPRACH short format may be considered for a TDD cell
with a very small coverage and may be configured to be transmitted
within symbols (i.e., the number of UpPTS symbols configured via a
SIB) forming an UpPTS or in one UL subframe. In this instance, the
corresponding preamble may be transmitted with a single-tone, or
transmitted with a multi-tone. Hereinafter, the Method 6 is
described in more detail by way of example.
Embodiment 1
[0438] For example, considering a NPRACH format that can be
transmitted within UpPTS 3 symbols, as illustrated in FIG. 35, the
NPRACH format may be configured to have 15 kHz subcarrier spacing
and consist of two symbols of 66.66 us and a CP of 33.33 us.
[0439] FIG. 35 illustrates an example of a short NPRACH preamble
format proposed by the present specification.
[0440] Even in this case, similar to the above methods, an implicit
guard time may be configured to be longer than a CP length, in
order to maintain a cell coverage due to the CP length.
[0441] That is, because a sum of lengths of a symbol group and the
CP is 166.65 us (i.e., 66.66*2+33.33 (us)) and a length of the
UpPTS 3 symbols is 214 us (i.e., 71.33*3 (us)), the implicit guard
time is 47.33 us and the cell coverage due to the CP length can be
maintained.
[0442] If a short NPRACH preamble is transmitted with a multi-tone
(e.g., dual tone) and the multi-tone is a continuous/discontinuous
dual tone scheme, it may be illustrated as the following FIG.
36.
[0443] FIG. 36 illustrates another example of multi-tone NPRACH
preamble transmission proposed by the present specification.
[0444] Referring to FIG. 36, a total of k subcarriers from a
subcarrier n to a subcarrier n+k-1 have been allocated as frequency
resources for the short NPRACH preamble, and it illustrates how the
NPRACH preamble is transmitted according to the situation of UL/DL
configuration #1 of legacy LTE TDD.
[0445] A first frequency gap has a frequency gap equivalent to a
subcarrier spacing in a continuous dual tone scheme, and a second
frequency gap has a frequency gap equivalent to 6*subcarrier
spacing in a discontinuous dual tone scheme.
[0446] If the short NPRACH preamble is transmitted using this
method, there is a disadvantage in terms of PAPR. However, there is
an advantage of a reduction in a latency for uplink synchronization
of a UE that is included in a small cell coverage area controlled
by the corresponding base station, or UEs close to the base
station.
[0447] There is an advantage in that consecutive UL subframes can
be allocated for NPRACH preamble transmission of other UEs by
configuring the UEs close to the base station to be able to use a
preamble with such a short length in a special subframe.
Embodiment 2
[0448] In addition, considering that the short NPRACH preamble
format mentioned in FIG. 35 is transmitted within UpPTS 6 symbols,
it is illustrated as the following FIG. 37.
[0449] Even in this case, similar to the above methods, an implicit
guard time may be configured to be longer than a CP length, in
order to maintain a cell coverage due to the CP length.
[0450] That is, if it is considered that a sum of lengths of a
symbol group and a CP is 166.66 us (i.e., 66.66*2+33.33 (us)) and
two symbol groups and the CP are consecutively transmitted, a sum
of lengths of the two symbol groups and the CP may be 333.33 us,
and a length of the UpPTS 6 symbols may be 428 us (i.e., 71.33*6
(us)). Therefore, the implicit guard time is 94.66 us, and the cell
coverage due to the CP length can be maintained.
[0451] Referring to FIG. 37, a total of k subcarriers from a
subcarrier n to a subcarrier n+k-1 have been allocated as frequency
resources for a short NPRACH preamble, and it illustrates how the
NPRACH preamble is transmitted according to the situation of UL/DL
configuration #1 of legacy LTE TDD.
[0452] FIG. 37 illustrates another example of multi-tone NPRACH
preamble transmission proposed by the present specification.
[0453] Similar to the Embodiment 1 of the Method 5 mentioned above,
it may be considered that a first hopping of a legacy NPRACH is
maintained as it is, and a second hopping appears as a dual
tone.
[0454] In this case, a unit of repetition may be configured as a
dual tone of two consecutive symbol groups, and may be configured
to determine a tone to which a first tone will move through a
pseudo random hopping and transmit a second tone away from the
first tone by a certain frequency spacing as mentioned above. If it
goes beyond a configured frequency resource region, it may be
configured to wrap-around in the frequency resource region.
[0455] If the short NPRACH preamble is transmitted using this
method, there is a disadvantage in terms of PAPR. However, there is
an advantage of greatly reducing a latency for uplink
synchronization of a UE that is included in a small cell coverage
area controlled by the corresponding base station, or UEs close to
the base station.
[0456] There is an advantage in that consecutive UL subframes can
be allocated for NPRACH preamble transmission of other UEs by
configuring the UEs close to the base station to be able to use a
preamble with such a short length in a special subframe.
[0457] This embodiment has described the non-contiguous
transmission as an example, but it is obvious that this embodiment
can apply a concept similar to this to contiguous multi-tone NPRACH
preamble transmission.
[0458] (Method 7)
[0459] Method 7 is to reuse a FDD NPRACH preamble format in a TDD
NB-IoT system.
[0460] A shape of a NPRACH preamble that has been used in FDD is
the same as FIG. 9 mentioned above.
[0461] It may be considered that the NPRACH preamble of the FDD is
used as it is, but a specific portion (e.g., symbol boundary) of
the NPRACH preamble is cut and is transmitted in each UL
subframe.
[0462] In this instance, a method for transmitting the NPRACH
preamble according to U/D configuration (i.e., according to the
number and a combination of consecutive UL subframes) using a
preamble corresponding to format 1 may be differently configured,
and is illustrated as the following FIGS. 38 to 41.
[0463] That is, FIGS. 38 to 41 respectively illustrate other
examples of NPRACH preamble transmission proposed by the present
specification.
[0464] If this method is used, it is easy to detect the preamble
because more energy is transmitted to the same tone. Further,
because a numerology such as a CP length and a subcarrier spacing
is the same as a FDD preamble, it may be a benefit in terms of cell
coverage.
[0465] However, there may be a latency problem due to an increase
in a unit of a single repetition. However, even if there is a loss
in terms of latency due to characteristics of the NB-IoT system
with many fixed UEs, it may be appropriate to use the corresponding
method.
[0466] Even if the same effect can be obtained using format 0, the
use of the format 1 with the long CP length may be more desirable
for this method.
[0467] Characteristically, as illustrated in FIGS. 42 to 45, it may
be configured so that the UE transmits the NPRACH preamble by
delaying it by X us (e.g., 266.66 us).
[0468] In this instance, characteristically, a specific time
duration (X) value may be an integer multiple of a length of each
symbol constituting the NPRACH preamble.
[0469] FIGS. 42 to 45 respectively illustrate other examples of
NPRACH preamble transmission proposed by the present
specification.
[0470] In addition, it may be considered a transmission method
using as it is the transmission format corresponding to the case
where the number of consecutive UL SFs is one even in the U/D
configuration in which consecutive UL SFs exist.
[0471] That is, an example in which two consecutive UL SFs exist
based on FIG. 38 may be illustrated as the following FIG. 46.
[0472] FIG. 46 illustrates another example of NPRACH preamble
transmission proposed by the present specification.
[0473] Even when this method is used, the NPRACH preamble may be
transmitted by delaying it by a specific time duration. In this
instance, the X value may be an integer multiple of a length of
each symbol constituting the NPRACH preamble.
[0474] In addition, it is obvious that a principle of the method
can be used even in a different subcarrier spacing, a different
number of symbols in a symbol group, a different symbol duration,
and a different CP length from the FDD NPRACH preamble.
[0475] (Method 8)
[0476] Method 8 relates to a transmission method by combining
NPRACH preamble transmission related multi-tone and single
tone.
[0477] That is, the Method 8 is one of methods obtained by
combining the above proposed methods and is a transmission method
while repeating multi-tone transmission and single tone
transmission.
[0478] Characteristically, it is contemplated to use contiguous
multi-tone in the multi-tone transmission. This is because it is
advantageous to use contiguous tones in terms of PAPR.
[0479] When this method is used, there is an advantage in terms of
latency because a single repetition duration is shorter than when
only the single tone is used.
[0480] A combination (multi-tone+single tone) transmission method
of the multi-tone transmission and the single tone transmission for
the case of the Embodiment 2 of the Method 2 (method for changing
the number of symbols forming a symbol group of a NPRACH preamble
to two) is illustrated as the following FIG. 47.
[0481] FIG. 47 illustrates another example of NPRACH preamble
transmission proposed by the present specification.
[0482] In addition, it is obvious that a principle of the method
can be used even in a different subcarrier spacing, a different
number of symbols in a symbol group, a different symbol duration,
and a different CP length from the FDD NPRACH preamble.
[0483] (Method 9)
[0484] Method 9 relates to comb type multi-tone transmission of a
NPRACH preamble, wherein one symbol group includes K symbols.
[0485] That is, the Method 9 may arrange multi-tone in a comb type
at intervals of K tones and may consider that K tones are repeated
in the same form in a symbol group.
[0486] Because the method uses the same subcarrier spacing but
shows a similar shape to using different numerologies, there is an
advantage in a multi-tone case having a frequency gap of two or
more tones.
[0487] A comb type multi-tone method for the case of the Embodiment
2 of the Method 2 (method for changing the number of symbols
forming a symbol group of a NPRACH preamble to two) may be
illustrated as the following FIG. 48.
[0488] FIG. 48 illustrates another example of NPRACH preamble
transmission proposed by the present specification.
[0489] In this instance, a symbol group shape may be illustrated as
the following FIG. 49.
[0490] FIG. 49 illustrates an example of a symbol group shape
according to FIG. 48.
[0491] In addition, the methods of changing the subcarrier spacing
among the above-mentioned methods consider that a first hopping
spacing and a second hopping spacing are also increased.
[0492] To overcome a shortage phenomenon of frequency resources
generated in this case, a method, in which the second hopping
spacing is not changed even if the first hopping spacing is
changed, may be introduced.
[0493] More specifically, in a legacy NPRACH preamble, a subcarrier
spacing is 3.75 kHz, the first hopping spacing is 3.75 kHz, and the
second hopping spacing is 22.5 kHz (=6*3.75 kHz).
[0494] In this instance, if the subcarrier spacing is increased to
7.5 kHz by two times, the second hopping spacing may be configured
to be held at 22.5 kHz (3*7.5 kHz) even if the first hopping
spacing is 7.5 kHz.
[0495] Furthermore, the first hopping spacing (or first frequency
gap) does not need to be always equal to the subcarrier spacing.
The first hopping spacing may have a spacing equivalent to a
certain specific partial subcarrier spacing less than the
subcarrier spacing, or may be greater than the subcarrier
spacing.
[0496] The second hopping spacing (or second frequency gap) does
not need to be always held at six times the subcarrier spacing or
22.5 kHz. It is obvious that the second hopping spacing may be
greater or less than the corresponding value.
[0497] In addition, the above-mentioned methods may consider a
method of interchanging the first hopping spacing and the second
hopping spacing.
[0498] If four symbol groups are included in one repetition unit
and are called T1, T2, T3, and T4, respectively, a method of
interchanging the transmission order (i.e., frequency resource
location) between symbol groups may be considered as illustrated in
FIG. 50.
[0499] Because T2 and T3 are TDD in the above presented methods,
the number of consecutive UL SFs is insufficient, which inevitably
causes UL SFs to be transmitted non-consecutively.
[0500] When such a method is used, there may be a difference in a
second hopping spacing (e.g., 6*subcarrier spacing) between
consecutively transmitted symbol groups, and there may be a
difference in a first hopping spacing (e.g., subcarrier spacing)
between non-consecutively transmitted symbol groups.
[0501] Because the second hopping affects accuracy compared to the
first hopping, it may be advantageous in terms of performance upon
consecutive transmission.
[0502] FIG. 50 illustrates an example of a method of interchanging
the transmission order between symbol groups of a NPRACH preamble
proposed by the present specification.
[0503] In FIG. 50, an option A is a method of interchanging T2 and
T3, an option B is a method of interchanging T1 and T3, and an
option C is a method of interchanging T1 and T4.
[0504] In addition, two or more NPRACH preamble formats may be made
as in the legacy NB-IoT and may be configured per CE level by the
base station. However, the base station may be configured to
independently configure a numerology and a CP length of a NPRACH
preamble, the number of symbols in a symbol group, etc. according
to the CE level.
[0505] That is, it may be configured such that the base station
configures each of the above presented methods to the UE per each
CE level, and the UE itself selects and transmits a NPRACH preamble
according to the CE level of the UE.
[0506] Further, the base station may be configured to configure
frequency resources not to overlap each other per CE level (or per
NPRACH format).
[0507] In addition, multi-tone resources capable of transmitting a
multi-tone NPRACH preamble are defined so that they do not overlap
other multi-tone resources even in one tone, and thus it may be
configured so that there is no ambiguity when the base station
performs the NPRACH preamble detection.
[0508] Further, code division multiplexing (CDM) between the UEs
needs to be considered by scrambling a different value on each tone
considering the multi-tone NPRACH preamble, and a sequence that is
usable in this case may be configured to come in the form similar
to an UL demodulation reference signal (DMRS).
[0509] The scrambling sequence can be a PN sequence.
[0510] In addition, the following phase pre-compensation method may
be considered for the purpose of reusing a base station receiver
algorithm that has been used to detect a single tone NPRACH
preamble (i.e., in terms of a reduction in receiver
complexity).
[0511] As illustrated in FIG. 51, the phase pre-compensation method
is performed so that a phase of a symbol group transmitted to a
(K+1)th tone in a Nth symbol group when a NPRACH preamble is
transmitted with a multi-tone is the same as a phase that intends
to be transmitted to a (K+1)th tone in a (N+1)th symbol group with
a single tone.
[0512] If the phase pre-compensation method is performed, there is
an advantage in that the base station can use an existing single
tone NPRACH preamble detection algorithm as it is.
[0513] FIG. 51 illustrates an example of a phase pre-compensation
method for multi-tone transmission of a NPRACH preamble.
[0514] FIG. 52 is a flow chart illustrating an operation of a UE
for transmitting a NPRACH preamble proposed by the present
specification.
[0515] More specifically, FIG. 52 illustrates an operation of a UE
transmitting a narrowband physical random access channel (NPRACH)
preamble in a narrow band (NB)-Internet of things (IoT) system
supporting a frame structure type 2.
[0516] The NPRACH preamble used in the present specification
includes at least one preamble, and one preamble may mean symbol
group(s) included in a specific duration.
[0517] Here, the specific duration may represent one repetition
unit.
[0518] The one preamble may include four or six symbol groups in a
NB-IoT TDD system.
[0519] First, the UE receives, from a base station, control
information related to an uplink-downlink configuration in
S5210.
[0520] The control information related to the UL/DL configuration
includes information about UL/DL configuration(s) supported by the
base station.
[0521] Particulars about the UL/DL configuration refer to Table 1
and a related description.
[0522] Afterwards, the UE transmits, to the base station, the
NPRACH preamble based on parameters related to a NPRACH preamble
transmission related to the received control information in
S5220.
[0523] The NPRACH preamble may include one or more symbol
groups.
[0524] One symbol group may include one cyclic prefix (CP) and at
least one symbol.
[0525] The parameters related to the NPRACH preamble transmission
may include a first parameter representing a number of symbols
included in one symbol group and a second parameter representing a
length of the CP included in the one symbol group.
[0526] The first parameter and the second parameter may be
configured to be different from a third parameter and a fourth
parameter respectively corresponding to the first parameter and the
second parameter.
[0527] The third parameter and the fourth parameter represent
parameters related to a NPRACH preamble transmission supported in a
frame structure type 1.
[0528] That is, the third parameter represents a number of symbols
included in one symbol group supported in FDD (or frame structure
type 1), and the fourth parameter represents a length of a CP
included in the one symbol group supported in the FDD.
[0529] Further, parameters related to the NPRACH preamble may be
differently configured according to uplink-downlink configuration
information supported by the base station.
[0530] The uplink-downlink configuration information may include at
least one UL/DL configuration of UL/DL configurations (indexes 0 to
6) stated in Table 1.
[0531] The third parameter and the fourth parameter may have a
value less than the first parameter and the second parameter,
respectively.
[0532] In particular, a value of the third parameter may be a
natural number less than 5.
[0533] The symbol groups may be transmitted through a first
frequency hopping and a second frequency hopping.
[0534] A value of the second frequency hopping may be six times a
value of the first frequency hopping.
[0535] For example, the value of the first frequency hopping may be
1, and the value of the second frequency hopping may be 6.
[0536] The parameters related to the NPRACH preamble transmission
may further include a fifth parameter representing a number of
consecutive symbol groups included in one preamble and a sixth
parameter representing a total number of symbol groups included in
the one preamble.
[0537] Here, the one preamble includes symbol groups included in a
specific duration and may include four or six symbol groups.
[0538] The specific duration may be represented by a repetition
unit, a preamble repetition unit, or the like.
[0539] For example, a value of the fifth parameter may be 2, and a
value of the sixth parameter may be 4.
[0540] The detailed description thereof refers to the Method 3
mentioned above.
[0541] Overview of Device to which the Present Invention is
Applicable
[0542] FIG. 53 illustrates a block configuration diagram of a
wireless communication device to which methods proposed by the
present specification are applicable.
[0543] Referring to FIG. 53, a wireless communication system
includes a base station 5310 and a plurality of UEs 5320 located in
a base station area.
[0544] The base station and the UE each may be represented as a
radio device.
[0545] The base station 5310 includes a processor 5311, a memory
5312, and a radio frequency (RF) module 5313. The processor 5311
implements functions, processes, and/or methods proposed in FIGS. 1
to 52. Layers of a radio interface protocol may be implemented by
the processor 5311. The memory 5312 is connected to the processor
5311 and stores various types of information for driving the
processor 5311. The RF module 5313 is connected to the processor
5311 and transmits and/or receives a radio signal.
[0546] The UE 5320 includes a processor 5321, a memory 5322, and a
RF module 5323.
[0547] The processor 5321 implements functions, processes, and/or
methods proposed in FIGS. 1 to 52. Layers of a radio interface
protocol may be implemented by the processor 5321. The memory 5322
is connected to the processor 5321 and stores various types of
information for driving the processor 5321. The RF module 5323 is
connected to the processor 5321 and transmits and/or receives a
radio signal.
[0548] The memories 5312 and 5322 may be inside or outside the
processors 5311 and 5321 and may be connected to the processors
5311 and 5321 through various well-known means.
[0549] Further, the base station 5310 and/or the UE 5320 may have a
single antenna or multiple antennas.
[0550] FIG. 54 illustrates a block configuration diagram of a
communication device according to an embodiment of the present
invention.
[0551] In particular, FIG. 54 illustrates in more detail the UE
illustrated in FIG. 53.
[0552] Referring to FIG. 54, the UE may include a processor (or
digital signal processor (DSP)) 5410, an RF module (or RF unit)
5435, a power management module 5405, an antenna 5440, a battery
5455, a display 5415, a keypad 5420, a memory 5430, a subscriber
identification module (SIM) card 5425 (which is optional), a
speaker 5445, and a microphone 5450. The UE may also include a
single antenna or multiple antennas.
[0553] The processor 5410 implements functions, processes, and/or
methods proposed in FIGS. 1 to 52. Layers of a radio interface
protocol may be implemented by the processor 5410.
[0554] The memory 5430 is connected to the processor 5410 and
stores information related to operations of the processor 5410. The
memory 5430 may be inside or outside the processor 5410 and may be
connected to the processors 5410 through various well-known
means.
[0555] A user inputs instructional information, such as a telephone
number, for example, by pushing (or touching) buttons of the keypad
5420 or by voice activation using the microphone 5450. The
processor 5410 receives and processes the instructional information
to perform an appropriate function, such as to dial the telephone
number. Operational data may be extracted from the SIM card 5425 or
the memory 5430. Further, the processor 5410 may display
instructional information or operational information on the display
5415 for the user's reference and convenience.
[0556] The RF module 5435 is connected to the processor 5410 and
transmits and/or receives an RF signal. The processor 5410 delivers
instructional information to the RF module 5435 in order to
initiate communication, for example, transmit a radio signal
configuring voice communication data. The RF module 5435 consists
of a receiver and a transmitter to receive and transmit the radio
signal. The antenna 5440 functions to transmit and receive the
radio signal. Upon reception of the radio signal, the RF module
5435 may transfer a signal to be processed by the processor 5410
and convert the signal into a baseband. The processed signal may be
converted into audible or readable information output via the
speaker 5445.
[0557] FIG. 55 illustrates an example of a RF module of a wireless
communication device to which a method proposed by the present
specification is applicable.
[0558] More specifically, FIG. 55 illustrates an example of an RF
module that can be implemented in a frequency division duplex (FDD)
system.
[0559] First, in a transmission path, the processor illustrated in
FIGS. 53 and 54 processes data to be transmitted and provides an
analog output signal to a transmitter 5510.
[0560] In the transmitter 5510, the analog output signal is
filtered by a low pass filter (LPF) 5511 to remove images caused by
a digital-to-analog conversion (ADC), is up-converted from a
baseband to an RF by an up-converter (mixer) 5512, and is amplified
by a variable gain amplifier (VGA) 5513, and the amplified signal
is filtered by a filter 5514, is additionally amplified by a power
amplifier (PA) 5515, is routed through duplexer(s) 5550/antenna
switch(es) 5560, and is transmitted through an antenna 5570.
[0561] Further, in a reception path, the antenna 5570 receives
signals from the outside and provides the received signals, and the
signals are routed through the antenna switch(es) 5560/duplexers
5550 and are provided to a receiver 5520.
[0562] In the receiver 5520, the received signals are amplified by
a low noise amplifier (LNA) 5523, are filtered by a bans pass
filter 5524, and are down-converted from the RF to the baseband by
a down-converter (mixer) 5525.
[0563] The down-converted signal is filtered by a low pass filter
(LPF) 5526 and is amplified by a VGA 5527 to obtain an analog input
signal, and the analog input signal is provided to the processor
illustrated in FIGS. 53 and 54.
[0564] Further, a local oscillator (LO) generator 5540 generates
transmitted and received LO signals and provides them to the
up-converter 5512 and the down-converter 5525, respectively.
[0565] In addition, a phase locked loop (PLL) 5530 receives control
information from the processor to generate the transmitted and
received LO signals at appropriate frequencies and provides control
signals to the LO generator 5540.
[0566] The circuits illustrated in FIG. 55 may be arranged
differently from the configuration illustrated in FIG. 55.
[0567] FIG. 56 illustrates another example of a RF module of a
wireless communication device to which a method proposed by the
present specification is applicable.
[0568] More specifically, FIG. 56 illustrates an example of an RF
module that can be implemented in a